I'm hardly an authority on BP wpns, but if you'd like a first rate quality production BP piece that you won't outgrow, look for one of the now discontinued JONATHAN BROWNING MOUNTAIN RIFLES (.54 first choice & .50 second choice) or one of the old Parker-Hale made ENFIELD MUSKETOONS sold by Navy Arms (a ready made sporter in .58; not one of the later Italian made copies).
You will still see them advertised in GUNLIST and run across them in gunshows from time to time.
A pretty standard choice and generally sound quality is THOMPSON CENTER. Hardly authentic, but close enough to be acceptable in a hunting rifle unless you're a purist who dresses the part and the TC's have durable modern designed locks.
Admire your choice of the traditional style rather than the new in lines which seem little different to me than hunting with centerfire pieces.
Hold off on the flinch-rocks 'til you've shot percussion a bit. The delayed ignition can be disconcerting 'til you get used to it and it requires a little more attn in the woods to ensure your piece shoots when you want it to do so.
Shooting BP is like everything else: you get what you pay for. Both of these pieces will shoot as well as you can hold if you do your part in finding loads and holding well. Ease of cleaning isn't related to manufacturer unless you deal with the crudest pieces, though having a keyed takedown in the "Hawken" style is preferable and simpler to clean to me.
One opinion, in the FWIW Dept and oughta be good for 2 cents at least.