V3m behaves like that when you plug usb, i.e. it attaches the storage by default and kills any running app that uses the sdcard. v3 didn't do this by default, you had to click on the interface to use storage. As for disappearing apps, if you unmount or reboot and the app doesn't come back, that would be a bug.
The fact is that using usb storage like that is obsolete and that may partially explain why cm11 isn't supporting it flawlessly. The "correct" way nowadays is for the kernel to provide MTP/MTD support and the UI uses that. With that implemented, USB storage doesn't need to be switched between android and usb, it's used concurrently (and safely I may add). Android won't kill apps running on the sdcard and so they won't disappear, not even momentarily.
There are two requirements to have that: our kernel currently lacks (AFAIK) this support *and* it should be supported by the rom too. I have no clue if CM11 implements that and what would be needed to have that working, all I know is that my wife's moto e have this implemented in it's kitkat and it works great.
Also there's the behavior in v3m that it automounts. I don't know if that's mandated by cm11 nowadays or if maybe @Zn7mkUKzN1r8aCIV tweaked some option when building the rom.
EDIT: It seems that you can go to configuration -> applications -> press the "..." on upper right -> usb connection and disable mass storage if all you want is charging mode.
If someone is close to the computer and want to try if either mtp or mtd works, please do so. I know at least one of then is not implemented in our kernel but the other should. Linux supports both, I think recent windows too, please try.
---------- Post added at 07:57 PM ---------- Previous post was at 07:44 PM ----------
Wifi or 3g? Moderate or light usage?
Other thing, the
Data Usage on configuration crashes upon entering that section, I believe this is not v3m related but more cyanogen issue...
Need to change it since my data plan has been updated and will stop my data service before I use all the mbs provided.