Andreas:
I'm happy to share my knowledge with you as best I can, so we'll go through your questions point by point.
Clothing and Arms
I don't THINK that there was a huge difference in clothing, especially among more military types, within the ranks of the Reiters depending upon your place of origin. There may have been at first, and perhaps a company raised in Meißen would have had slightly different fashions than a company from, say, Darmstadt, but all in all I don't think that the differences would be that noticeable to say a French peasant being plundered of his goods. Even more so after campaigning for a season or two.
1 - Combat Wear and Arms
I think that you have the basics well in hand for this, other than the possibility/probability that Germans would have generally preferred pluderhosen to other forms of upper hosen, and of course worn with boots and spurs for mounted work. However, all sorts were seen in period illustrations, so it's more a matter of personal taste, and deciding if you want to go with the most common for your impression, or what you like better. I recommend Jost Amman's
Illustrations for Artists and Illustrators (1568) which at least used to be available from Dover Books.
At the time, it doesn't seem as though there were often specific arming doublets much in evidence, and often as not (perhaps even more often) armour was worn over one's day to day clothing. Thus you wouldn't require a separate set of clothing for camp or the march, as they would be the same clothes worn for combat. And a beaver hat and replace the boots with shoes if doing much on foot, and you have your complete wardrobe.
Arms and Armour: Suit of 3/4 armour, helm of burgeonet type with no visor or falling buffe, brace of pistols, possibly a cavalry carbine of some sort, shavionna or other basket-hilted sword, dagger (of quillon or bollock variety).
Other than the carbine, I think you're fine with this selection. Cavalry was forming up into several distinct types at this point, and most German-style Cavalry (meaning Pistoliers in particular) was armed only with a pair or more of pistols and swords. However, they often had in the same command a group of Harquebusiers, who would be armoured in breast, back, gorget and a light helmet, and armed with carbine, pistol(s) and sword and mounted on a lighter horse. But they were definitely considered inferior to Pistoliers/Reiters for most purposes (other than for guards, raids, dismounting to fight on foot, etc., i.e. the stuff that later Cavalry specialized in.) I would also expect that many if not most of those equipped with burgonets would have a buff of some sort, as the face was the favorite target for lances, swords and pistols.
3 - Dress Clothes
Shirt (finer, with embroidered cuffs and collar, underpants (short, as modern briefs), high-quality pluderhosen and doublet, fancy hat, latchet shoes. Sword, dagger (of quillon or bollock variety).
Sounds good. Always nice to have dress clothes in case you have to meet someone important, like your employer (i.e. the King of France, Spain, Navarre, etc.)
Note that I didn't mention socks - this is because I'm unsure about how they were done. Knitted or sewn stockings would work, but the woodcuts (from Meyer's Kunst des Fechtens) and paintings seem to indicate sewn hose - how would those be worn or attached? I can think of about three or four different ways to do it, but I'm not sure which would be correct.
Technically they should be sewn hose, though knit hose were coming into fashion (but were expensive). Some hose was attached by points (see some of the woodcuts by de Gheyn in "Exercise of Arms"), but usually just gartered up under the knee.
Questions of Outfitting
What is a 'brace' of pistols?
Just an antiquated term for pair. As in "A brace of quail for lunch" or something like that. Two.
What manner of pistols (or firearms in general) would have been used? I'm thinking matchlock or wheellock, but I know very little about period firearms.
Okay, now it gets both simple and complex. The simple is what they used. Wheellock pistols, pure and simple. Snaphaunces were known to the Scots and English, and were novelties pretty much everywhere else, while matchlocks make fine Infantry weapons but pretty poor Cavalry weapons. Wheellocks were during the 16th and first half of the 17th Centuries considered to be the
ne plus ultra of Cavalry arms. In fact, in France, it was illegal to use any other form of ignition system on a pistol until some time in the 17th Century.
The complex part is acquiring them in the here-and-now. Not many makers of such clockwork toys about at the moment. Sadly my own gunsmith Dale Shinn is retiring, much to my dismay, with no one really able to fill his shoes. There are a couple of fellows able to make wheellocks out there, both in the US and Europe, but they are quite expensive. On the other hand, I recently discovered that an English outfit is now importing a wheellock pistol from India. Made on the same lines as the Jacobean-lock (sometimes called "doglock") pistol imported by several US and Canadian firms, it's a tad late for actual Reiters, being much more of a 1620's to 1650's piece, and bloody expensive by comparison to the Jacobean lock pistols (£600 as opposed to $300). But here it is:
http://www.derbyshirearms.co.uk/pages/latest_news.html
On the other hand, there is a Czech outfit that may be worth looking into:
http://www.czechstyle.com/index.php?cPath=17_81
BTW, for English and Scots in the Lowe Counties, one could modify the Jacobean lock pistols for use, but no one else seems to have used Snaphaunces/flint-ignited pistols with much regularity otherwise.
What manner of tent would/could have been used? Bell tents and pavilions come up a lot, what about wedges and double-belled wedges?
I'm sure plenty of odd-ball tents were used, but most of the illustrations have been of bells and round-end marquee tents.
Would or could a shield of any type have been carried or used, and of what type? A steel target/rotello or buckler seems to be the most likely, if at all plausible. I know Reiter were cavalry (hence the name), and predominantly pistoleers, but if forced to fight on foot for whatever reason (horse killed, etc), would or could a shield have been used? If "could" is the answer, how unlikely is that "could"?
Certainly a Reiter wouldn't dream of carrying such an impediment with him on his horse, as managing the horse and pistol in armour is sufficiently absorbing an activity, but perhaps if they expected to be used as assault infantry during a siege the might have some steel targets in their baggage. I've yet to read anything specific about it, as most of the targets were used by Foote officers for such things as siege work, but as many extant garnitures of armour included targets, it stands to reason. Certainly would be a good excuse to have on in your inventory of you choose to do any SCA Heavy Fighting in your Reiter rig.
Questions of the Period
When on campaign, would he have servants/men at arms of any sort to assist him? I understand that Reiters were likely to be not as well-off as some and so probably not have a whole posse to tail them around, but one or two pages or servants (perhaps a cook) could be of good assistance.
Absolutely. In fact even the lowly Harquebusier was allowed a "Boy" to ride his spare horse, and to take care of basic camp chores for him. From personal experience, trying to care for and saddle your horse and put on armour in anything like a timely fashion is near to impossible. Most such Reiters, if they were at all well off or born, would have had at least one and probably many servants. One of the things noted about Reiter regiments was that they always managed to keep their strength (in numbers) close to their contract's demands. Many spectulated that many times Boys on the spare horses were used to replenish the ranks of those Reiters who succumbed to disease or other non-martial maladies. A Reiter regiment's "tail" was often longer than the body, with plenty of servants, labourers, artisants etc.
Were there Catholic Reiters? The most predominant campaigns of the area and time, and the main one to which I've seen Reiters attached, are the French Wars of Religion. I understand that many were German protestants serving the French Hugenots. Were there Catholics Germans (Reiters possibly) serving the Catholic forces.
There indeed were both Catholic and Protestant Reiters, and respectively in the employ of Royalist/Catholic League and Huguenot leaders during the French Wars of Religion. At Ivry in 1590, the duc de Mayenne had Catholic Reiters under Eric of Brunswick unsuccessfully trying to complete a
caracole, while in the opposite army, Henri of Navarre had a similar corps under Dietrich of Schomberg, who after discharging their pistols charged headlong into the enemy line and smashed it. Although they did not fight directly opposed to one another, both Catholic and Protestant Reiters were present at that battle.
Also, where was the Holy Roman Empire fighting in 1570-1580?
Pretty much all of their official energies, such as were spent on warfare, were aimed at the Turks, campaigning in Hungary.
Sorry for the length, but I've been composing this for some time.
No worries, happy to be of service. Perhaps Chef or some other student can add to my brief answers. And please feel free to ask more of them.
Cheers!
Gordon