AOSP NeatROM hasn't been maintained for a long time now. I wouldn't recommend it if you really want to make your S2 "new". It was released long before Stagefright security issue became prominent and also before the infamous freezebug was fixed. Probably there are other unfixed issues. I would recommend trying CM12.1 or another CM12.1-based rom, which is still well maintained.
Not sure what exactly you mean by the USB-storage stuff. I never had problems with this, no matter if stock or AOSP rom.
Hm havent checked that one out yet. Is that a lightweight rom and with good battery life?
The USB storage im talking about is that the S2 has 2 different storage locations(3 if you add the optional sd card) The primary is 2 GB and thats where you install programs. In addition it has some sort of 11.5GB storage USB that can only be used when connecetd to a computer for photos etc. So its basicly a non usable USB stick on your phone. I was hoping that there now was a way to use that storage as a primary storage and for apps.