I got a LH 54 cal flintlock.
I say go with the 54. Tons of knockdown power.
If you shoot a lot like more than 200 rounds a year, maybe it makes sense to go with 45.
Lots of flintlock shooters by me prefer the 45. So, it's got enough snuff.
My advice. IF going with the GPR. Buy a L&R drop in replacemtn lock for it. Then sell you unused lock online.
The trigger, barrel, and wood are good on the Lymans, atleast mine it is.
Pick up a 40 cal brush to clean the patent breech section of the gun.
If going flint, buy a new 1/16" drill bit and enlarge the flash hole. Buy a spare flash hole.
The stock lock works, but there are better ones out there. The buy and sell your stock upgrade will probably only set you back another $75. Well worth it.
IF using the stock lock, get the flint as close to the frizzen as you can. Put a small twig to bring the flint closer.
Also, having the flint straight edge be on top increase the arc of contact with the frizzen. Helps with more spark.
If going percussion, I haven't seen anyone complain about a snap cap GPR.
I have doen very well with my stock GPR at woodwalks.
Also, replace the adjustable rear sight with a fixed one. The sight walks around a bit, but isn't ever off by much. Just enough to miss really small targets at woodwalk shoots. not enough to make problem with a deer at 75-100 yards, or miss a small paper plate.