There are several conicals you can try if you're so inclined gtonini. As Johnmorris stated, there are about a half dozen PowerBelt models and weights in .54 caliber, as well as the 425 grain Hornady Great Plains bullet and the 420 grain TC Maxi-Ball. But I'm of the opinion that in .54 caliber a patched round ball will do all that needs doing on whitetails.
Swiss powder has a good reputation. I've never used it so can't say any more that that about it. It's the most expensive of the black powder options and not as readily available as others. I've used GOEX for years with no complaints.
I have three .54s that I shoot round balls from, two caplocks and a flintlock. The flinter favors 95 grains of GOEX FFFg under a patched ball. One of the caplocks shoots best with a hefty load of 105 grains of FFg. But all of my barrels have a slower twist rate than your Renegade, which has a rate of one turn in 48" (1:48"). I suspect you will get the best accuracy with something in the 70 to 80 grain range, which is plenty for whitetails out to 100 yards. You just have to do some careful shooting over a bench to find the load your barrel likes best.
Good luck, and let us know how you're doing.