Also consider that some states do not allow saboted bullets during their dedicated muzzleloader seasons but, I believe they're allowed during the regular seasons. This must be a consideration, as some will shoot conicals better than others. Although some of those rifles that won't shoot a conical good, they will shoot a Thor great. Another bullet option for those states not allowing sabots......
Big difference between a whitetail and elk but, I know hunters that have taken deer at 300yds. Muzzle velocity starts to drop and bullet energy drops off significantly too. I'm not an elk hunter but, someone should be able to tell you the minimum recommended bullet energy for elk.
I prefer shooting Blackhorn 209 propellant. There are a ton of reasons for that. I'd highly suggest you consider it but, make sure when purchasing a muzzleloader that the breech plug is designed to shoot it. Many of the CVA rifles require either a replacement breech plug or modification. T/C rifles need no modification and will shoot it right out of the box. Blackhorn 209
I'm partial to the T/C Pro Hunter and have been a T/C shooter since the Encore platform came out. If..... I had the opportunity to hunt elk, my choice of propellant would be BH209, with CCI209M primers and I'd switch from my usual 250gr Barnes TMZ to the heavier 290gr Barnes TMZ bullets. With BH209 the maximum charge is 120grs (V). I currently shoot 110grs (V). If my groups held, I'd shoot the max 120gr (V) load.
Good luck with your decision.......... practice, practice, practice