If I understand it correctly...
I don't have to reset the hardware when switching card with the same account.
However, if I want to switch to another say, Japan account owned by me, I will have to reset the hardware. I will hit the same problems he mentioned.
As for wallpaper settings, you'll lose them when you pull out the memcard, even without switching account. To prevent this, put one default/system bubble per screen, the wallpapers should all remain intact. This trick won't work if you switch to a different account though.
That's right. When switching accounts, all persisted data inside the internal flash memory will be deleted.
Pulling out the memory card when the Vita is not completely turned off, is not recommended though. ;-)
Everytime the "state" of the Vita memory card slot changes (i.e. a card was plugged in or out or a card was replaced with another) before turning the Vita on, the "building database" operation is initialized and the whole process of rearranging the bubbles starts again.
The order of the bubbles is never random, it's always in the alphabetical order of the PCSB/PCSF/PCSI/etc. codes.