First off, I apologise for the late response but I just joined this forum recently (even though I've been visiting planet gamecube / nintendo world report for years).
Anyway.....
1. I can play this game on the Wii and the select screen seems to load faster. You do need to use the Gamecube Freeloader, although a certain version will not work, I don't remember which version. Just note that when you load it, it will reset, and then load it a 2nd (or in some cases a 3rd time) and it will work just fine.
2. NO, gamecube controllers only.
3. Don't know, never played Ex with a Wiimote, but I assume it would be better.
4. I like it, most would prefer the classic controller.