SureAI

I was sure I saw a mod which lets you play without the main quest, but can't find it anymore. Did I imagine it or does it exist?

Also, is Enderal able to be played past the main quest like Skyrim? I'm just wondering because I like Enderal almost better than Skyrim now.

What do you mean by "play without the mainquest"? If you don't want to do it, then simply don't. Or did you mean an alternative start?
Enderal has a point of no return, after which progressing in the mainquest will lead to the end of the story. Don't worry, the game will warn you explicitly when this happens, so you can finish your sidequests and exploring first.