Other than the higher cost, I can't think of any reason not to buy the Swiss powder. It screens well, and shoots well. Its just so much more expensive than Goex powder that its hard to justify the price.
As for loads, FFFg powders are higher pressure powders, and the standard rule is to reduce the volume of powder used by 15% from what equivalent charge you might use if you loaded FFg powder, or one of the substitutes for BP. You don't give us a caliber on the guns you shoot, and we don't discuss the In*&#$ things on this forum. So, without knowing what caliber you are shooting, and whether you are shooting Patched Round Ball( PRB )
or conicals, and then how much your conicals weigh, its hard to recommend a load. Basically, using any black powder, if you don't have a loading manual to use for a basic starter load, the old recommendation was to use a volume of powder that is nominally the same " weight " as the caliber of the gun. Work up from there in 5 grain increments, until you find a load that works. I recommend using a chronograph for all such work up shooting, as it tells you much, and saves you time and money. If you have a specific question about a specific combination of components, please let us know. When you get down to real details, we have years of experience which can diagnose problems, and help you solve them without spending half your life trying one thing, and then another.