It's funny you should notice that, one of the inspirations actually was Evangelion. ^^;

1. The ability to be one is something innate that will be relevant later, the power level of a magitech girl is variable depending on the girl's self-confidence and synchronization with the gear(which has a lot to do with self-confidence).

2. Not as of yet, they don't.

3. Hm. I'm not entirely sure what kind of comparison I have in mind. I suppose I'd compare it to Nanoha(not the Nanoha supermodes, though) to start with? Not that we'll stay there as things go on.

4. Each Nephilim is unique, but for the most part it will probably take more then one magitech girl to take them out.

5. Again, each Nephilim is unique, so that depends. However, no conventional weapons are going to actually kill one, though they can help give the magitech girls a better chance. Nukes probably would be an absolute last resort, if anything.