Vortex Crossfire 1x-32, we can only use open sights or 1x scopes here in ND when you are drawn for a muzzle loader only tag. After hunting with my muzzy for the first time this year I would be comfortable shooting up to a 9x scope on it. I was able to put a nice group together at 200 yards even with a 1x scope.
I have a Knight Ultra light that I put a Leopold 2-7x33 on. A scope helps tremendously with developing a accurate load.I mounted the scope in quick detach rings so that I can hunt during the muzzle loader season with open sights then put the scope back on and hunt during the rifle season with the scope here in Colorado. Sabot loader has some great threads about switchable scope/open sight options for muzzleloaders.
I doubt a scope will ever be what limits your shot with a muzzleloader. I’d never mount a high dollar scope to mine. Find one with at least 4 power that can handle recoil and call it good.
It would depend how I was going to use it. Colorado doesn't allow scopes during ML season, but if they did I would want something with a very low bottom end on power for very close shots. My daughter's ML shot this year was 30 yards and a few years ago my buddy's shot was 7 yards....both elk. I think a 2-7 or even something like a 1-6 would be perfect.