I really don't plan on using 20A on either side. I was planning on
using the 20A mainly because I had the 12 gage wire & I was sticking
with the 12 gage because of my run length. I originally thought the
length would be about 170ft but I didn't take into account the routing
I had to do up and down to my outlet boxes and around things.

I would call the circuits light use with a TV, dehumidifier
(spring/summer) and possibly an electric space heater (occasionally) in
the winter. Maybe a computer and some lamps will eventually be down
there too but I don't plan on using really heavy draw power tools or
having a workshop down there or anything.

Lights are on a separate 15A circuit.

Thanks for your feedback!