Anything you make using your game made in EU4 directly or indirectly is subject to revenue and paying the 5% of gross.
Other users you speak about likely wouldn’t have a contract with Epic Games so this complicates things, but I assume anything they would earn would be ownership of Epic Games until a contract saying otherwise would be signed.
As far as I know recreating any game is possible as long as you don’t use same names for the title and in the game,
for example if you’d make a copy of FIFA soccer game, you’d need to change the title , and also the names of teams and players in the game, most times only 1 different letter in a word is enough.
If you’d remake Tetris game you couldn’t use names ending with tris , but you could name it Tekris or something like that.
I hope this helps.