If I were going to shoot a muzzleloader, I would want it to be a traditional style. A breechloader faked up into a muzzleloader like that Rolling Block does not appeal to me at all.
A friend has a .50 Kentucky/Pennsylvania rifle that is very nice and I would make the similar Pedersoli Frontier my first choice of your list.
Nothing wrong with an Enfield, built to be "soldier proof" it would serve well.
The Sharps is the only "capping breechloader" seen very often now. It is much different to manage than a muzzleloader. There is discussion on the Shiloh board:
https://shilohrifle.com/forums/viewf...de730997d6789d
Pedersoli makes a conversion for their percussion guns to take #209 shotgun primers.
https://www.cabelas.com/product/Davi...it/1608590.uts
There is a maker of little bushings to let you use rifle or pistol primers in a #209 device.
http://www.prbullet.com/lrvf.htm
Look for reviews, it is not always the way to go.