For example if I want to play Fallout New Vegas with DUST and switch to Nuclear Sunset.

I feel like having multiple installations of the same game is the easiest way if I have the space for it. They would both share the same FalloutNV folder for the INI files and save games and I'm wondering would this cause issues?

It would be easy enough to basically copy files back and forth when I want to play one version versus the other. Maybe a simple batch script that moves a FalloutNV folder into the My Games folder before running the game and, when the game is exited, moves the FalloutNV into the same directory as the game's executables.

I feel like the modding scene for Bethesda games is big enough that there must be an easy, more polished, solution to this.

I tried looking up solutions online but a lot of forums posts get wrapped up in Steam not easily allowing you to have two installs of the same game.

Some older posts recommend applications such as Skyrim Installation Swapper but it seems like people may have moved past them. There hasn't been a new comment in the post tab or update for years.

I imagine profiles and instances provided by managers could help but I don't know how well they do with hundreds of mods. Nuclear Sunset for example uses Tale of Two Wastelands as its base which I feel like could cause issues.