For the longest time, I wiped before a nandroid restore, now I understand that a nandroid restore, if made with Amon Ra, will auto wipe before restoring.
However, it does not hurt to wipe all except sd card before a nandroid restore and that's the way I will continue to do it before restoring.
And yes, your nandroid restore will bring all back to what is was depending on how you backed up.
As far as BFQ vs. Noop, I'm not sure.....
Hope that kinda helps you.

 

nandroid backups are kind of like save points in a game. and just like in any game save early and often. with phones i always recommend that you do a nandroid backup before you make changes to the phone ie flash roms, kernels and mods or themes. that way if something goes wrong or you do not like something, you can always go back.