A: That's a very subjective question that doesn't have an objective answer. It would probably sound like your modeler through a bass tuned cab; a little darker, richer tone than a FRFR cab.
Have you ever played your 6-string guitar through a bass amp?
Many of us here do, from time to time. The bass amp's EQ adds some rich warmth, as does the cab tuning. Although, some Rumblers find the R100 a bit boxy sounding and have to add some acoustic fill or lining, or at least put a sock in a port, to get the bass tone they really like. But, for guitar, you might not want that.
One
warning: the FX Return is unaffected by the Master volume control, so be sure you
start with a low level from your modeler! You should be able to try it like that at the store.
Let us know when you get your Rumble. I'd be happy to give you another distinguished Club number!