Welcome to the Forum.
The Ohio is one of the few Pecatonica River rifles I haven't built but I can say that Dick Greensides is a great guy to work with and he supplies high quality parts with his kits.
As you may, or may not know, the "kits" supplied by Pecatonica River, Track of the Wolf, Muzzleloader Builder's Supply, Chambers and a number of others are not "drop together" kits.
Actually, they are a box of unfinished or semi-finished parts with the lock and set trigger being the only operable parts. Everything else has to be hand fit finished and assembled.
The builder of any of these "kits" should plan on spending at least 150 hours working on his/her kit to make a finished gun.
Now that that is out of the way, you may notice that Dick offers the Ohio with a cheek piece on BOTH sides of the stock or no cheek piece at all.
I would suggest that you order the stock with both. If you later decide you don't like having a cheek piece on the "wrong" side of the stock you can always file/sand it off.
Actually, quite a few of the Ohio guns had the cheek piece on both sides although I'm not sure why.
OHIO STYLE HALFSTOCK RIFLE LINK
This kit uses an L&R Ohio Warranted Percussion lock and the stock will come with the lock mortice pre cut for you. I don't know of a Flintlock that would fit that mortice so if you want a Flintlock Rifle this is probably not the gun to choose.
If you like Percussion guns this one will be fine.
Also, it isn't real clear in Pecatonica River's web link, this is a half stock rifle. Personally I like both half stock and full stock rifles and I'm only mentioning this because some people might get the idea from the picture in the link that it a full stock style rifle.
If you would rather have a fullstock rifle in either percussion of flintlock I would recommend the Leman Fullstock gun. The difficulty in building it would be about the same as the Ohio Rifle.
LEMAN FULL STOCK RIFLE
Whichever rifle you finally decide on, you are doing the right thing. Right now is the time to study all of the possible gun styles to decide which one you like the best.
As much work as is involved in building one of these guns you want to be sure you have exactly what you want before you order it.