A sleeping bag can be a pain to get into...
For TQ's there are cheap simple ways to make one.
I use a poncho liner,($16) and put shock cord in one end to make a foot box. The poncho liner is lightweight but it does keep me warm. I would rate it a 50*.

When it's cold I double it up with a lightweight sleeping bag that I us as a TQ. This sleeping bag was only $29 and it had shock cords up by the shoulder area and top of the bag and a Velcro tab to close it up. It unzipped all the way open, so it was easy to convert to a TQ.
I think it is rated at 50*
when I double it up with the PL I stay warm in 20-30* weather