It's probably my best option. I already use my primary Google account for another GV number but I suppose I can open another Google account and port my TMO number there?

Or is it possible to have two active GV numbers on one account? The docs are unclear.

Seems like I would transfer my TMO number to GV at which point my existing GV number would expire within 90 days, but I could pay $20 to make it permanent. Can anyone confirm from their own experience?