Neither of them will work in EasyRPG, not supported (AVI is planned because RPG Maker 2000 supports movie playback, but we don't support this yet)
It would have exactly the same bugs as EasyRPG for Windows, so nothing to worry here
Because you know nothing about C++: Very likely, you will need at least a few weeks to understand the basics of it on the other hand custom battle systems are lots of work to write, too.
We plan to extend the Player someday with new functionality (not provided by RPG2k) and finish our editor but this is still under development. We are just a small team which does this all in our freetime, therefore everything takes much longer then in a company with full-time workers.