RE: NewB here...
My Disc rifles like loose Pyrodex RS and Triple Se7en 2f. When I shoot Pyrodex I shoot 120 grains of it and a 250 gr shockwave. It also shoots XTP's very well. When I shoot Triple Se7en I shoot 110 grains of that.
My Disc rifle is older technology to the one you're getting but they are good shooters all the same. If you ask Knight want to shoot they always tell you two pellets and Knight Red Hots.
Good luck with your rifle.