to be honest, trying out the minor factions one by one is probably the best way to really get to know what they do and how they affect the difficulty. Golems for example, are superweapons. Medium and hard merely gives the AI something in return to counter those superweapons, while easy basically just gives them to you without consequenses. Personally I prefer golems medium, since it raises the AI progress each time you repair a golem, which can cause a lot of extra "fun", especially on higher difficulties.
But yeah, in general golems make the game easier. Unlike roaming enclaves for example, or rocketry corps, which can be a serious pain. And don't even get me started on the Ai plots. Even after more than 500 hours of playtime, I still avoid some of them (darn hybrids).
If you really want to figure out how to make things easier or more difficult, trying out all the AI types is a really good idea.
but I'm afraid there is no list as to what influences the difficulty and how much. There are a lot of different things that influence the difficulty (map style, AI types, starting location, minor factions, plots, fog of war, ship types) and it's different every single time. The map generator can also really screw people over sometimes.
so yeah, I guess it's just a matter of experiencing yourself ^^