"Ideally, it would be a menu-based choice system in the game set-up. I
fear the playing around in the "My PC" section of Windows."
The mod-picker program handles this, once you get it installed. Really though, it's nothing complicated
With TDM, you just unzip to your SE4 folder. IIRC the TDM path.txt will then replace your original path.txt. That makes SE4 use the TDM mod.
Phoenix-D