The only things you must install before the KA Mod are the v1.042 patch (Unofficial one recommended), and Ancient Disc mod if you want to use it. The KA Mod checks for the Disc mod during installation, and will ensure that the Disc mod still works later.
User Error and the Complete Map Pack can be installed at any time, before or after.
You can have as many mods as you want, but only one can be active at a time. The Disc mod working together at the same time as KA is a special case, I deliberately designed KA to work together with the Disc mod so both are enabled at once.
Maps are different from mods, and are just active all the time once installed.
There are only two versions of KA, so far: v1.0 and v1.1. v1.0 is old, outdated, and hard to find. v1.1 is the current version and easily available. v1.0 and v1.1 are not compatible with each other when playing online.
There is no reason to get v1.0, v1.1 is much better in every way.