I’m new to muzzleloading and wonder what’s the difference betweeen these 2 products and where can I buy them ? I have a knight .50 cal disc rifle. Where can I find load information ? Thanks for the help and do these products come in pellets or loose powder ? Thanks for the help and input.

Since neither is black powder, we should have another section for non black powder rifles.
Anyway, I actually do use some 777 and it works fine. However, none of the modern stuff will perform as well as real black powder. Try some in a flintlock and you will see; won't work.
Loads? What caliber do you have? 80-100 grains is fine for 50 and 54. Look on the internet. Loads for these are not critical like smokeless cartridge ammo. Five grains is nothing.
You don't actually weigh it; you use a volume measure. BP equivalent.
What bullets are you using?
Pellets? I don't use them; they are a crutch; anyone can measure powder.
You can order it. Or Dicks sporting goods; places like that.
I actually do have a .54 TC inline that I load 100 grains of 777 in with a 451 sabot bullet. Like shooting a 30-06 up to 200 yards; I would ban them if I could. Too late now; young guys won't clean a real BP rifle. I was at Friendship two years ago and they actually have a category for inlines.
You can see I am an old black powder shooter way before we got inlines which should not even be classified as muzzle loaders. I know......No hate mail; I get enough now.

These are muzzle loaders I built. Among many.