Settings will be unaffected by your import (in fact, the style settings to your v7 are completley differant than your .c, nothing "style"wize will be imported.
The classic importer will create the users based off of your .c install.
If it's just a test, go ahead and import with your forum open, i did it while testing the importer during alpha/beta.
Importer imports everything.
It'll take a good chunk of time, i'd start it before bed
... it'll give you a suprise when you wake up!
as for space used, i think .t would be double, as posts are stored twice in the database (one formatted, one raw)
