I've tried Swiss, Wano, Goex and Elephant... And that's the decreasing order of their quality! Pre-2000 Elephant was sometimes very bad (inside of cans corroded, then then used crappy plastic cans for a while which cracked during storage) but the newer stuff is OK... I mainly used the stuff in cannons and in smoothbores so fouling or precision were not real issues! Swiss is great in rifled arms...
Swiss is (or at least was!) imported in the USA by Schuetzen Powder in Texas and is distributed by many outfits in the USA... The Maine Powder House was my place to buy powder before all the new post 9-11 hysteria... Or we picked up a crate or two when down in Virginia for one of the Civil War shoot! Good old days! I'm not sure now if you still can buy BP in cans in the USA as a tourist... I think it is not considered ammunition but one would have to check!