Re: Separating the game and mods
@lucainato What drives are you talking about here? The way Sims 4 is programmed, it can't take advantage of the speed of an NVME solid state drive over a SATA SSD, although both are an improvement over a mechanical drive (HDD). So if D is any kind of SSD, it doesn't really matter what's on D and what's on E—the limiting factor will be the game itself.
If D is an HDD, whether it helps more to move the game's program files to E or the user folder (or just the Mods folder) depends on how much is in the Mods folder. If it's a lot, then having Mods on E will likely be more beneficial; if it's a little, it would be better to move the game's program files to E. I can't really tell you where the line is though because it's about both the amount of custom content (not so much mods) and the type. You may also notice different results for the initial loading screen vs. travel transitions.
If you're not sure, I would suggest experimenting a bit. And if you don't actually notice a difference, you don't really need to worry about a few seconds gained or lost here or there.