[Slick]

You do not need to have different installs of SE4 unless you are using mods that require different Versions of SE4. Most mods have been updated to the latest SE4 revision, so you probably can just use the latest Version. Mods each go in a unique subdirectory and most mods use .zip or installers that put the files in the right places.

The modpicker is on your SE4 Gold CD. There is an updated Version posted here in the upload section. Search for Matryx's mod picker.

Different people like different mods, you will have to make up your own mind. Most mods have a readme or similar that gives an overview of the mod. Most of the bigger mods also have a discussion thread here in the forums.

In general, mods cannot be combined. If 2 mods do not modify the same files, they could be combined, but even in those cases the AI might not work as intended. There is a file on the SE4 Gold CD for identifying conflicts. Some mods have instructions on combining with other mods. Additionally, if you want to combine mod A and mod B, you probably want to install mod A and mod B and then create a 3rd folder for mod A+B so that you can still play them individually. For details on combining 2 different mods, I suggest you go to the mod threads here first and/or contact the mod creator(s).

Slick.