Really, any powder you use will be fine, and if you can seat the ball, your load is safe. Not necessarily accurate, but using any black powder or black powder substitute it is nearly impossible to overload unless you are just intentionally trying to blow your gun up. This includes Triple 7, which I really like! You only need to reduce loads by 15% with 777 to get Goex performance, a full load compressed (another tale that gets reported, that you can't compress 777, it only is not to be compressed for METALLIC cartridge reloading). I prefer at least a .454 ball to get a better seal, and more "grip" on the rifling. A .451 works OK, but gets less velocity, and in my guns, is less accurate. I use regular old Crisco or off-brand shortening for my over ball lube. In a .44, I like to use at least 28 grains (always measure by volume), anything less and I get inconsistent results due to a lack of compression. I could use a filler, but that is just another step I don't want to hassle with. A full house load will wear your gun out more quickly, and the wedge pin will show wear if you are always using max loads. I use 28 grains of whatever for target shooting, and 35 grains, usually 777 to get maximum velocity for hunting. If using bullets, I do reduce my powder charges, but 98% of my shooting is with round balls. I never have made cartridges, I know fellas who do, but just another thing I don't want to mess with. Here is some velocity data from my .44's. This data is compiled from a lot of shooting over a chronograph.
8" barrel .454 round ball
28 gr. Pyrodex RS 800 fps
35 gr. Pyrodex RS 980 fps
28 gr. Pyrodex P 860 fps
35 gr. Pyrodex P 990 fps
28 gr. Goex fffg 820 fps. (very consistent shot to shot)
35 grain Giex fffg. 959 fps (same)
28 gr. Swiss fffg. 880fps
35 gr. Swiss fffg. 1020 fps
28 grain 777 900fps
35 grain 777 1080fps
The 5" "Sheriff's Models" get about 150 fps less with the same loads. I often use Pyrodex RS, not for performance, but because years ago I got a bunch of it (40 some bottles) for $1 a pound at Walmart end of season clearance. Those days are long gone!