I have both a Zpacks 20deg in regular/wide, and an EE 40 deg quilt in regular/wide.
I have used the Zpacks down to about 20 degrees, but it was pretty cool, and I wished I had more insulation (like a nice down jacket). On the other hand, unless it's down in the 30s, I was was too hot. My version is the full side zip version, but I too use my feet poked out for air conditioning, and that isn't really an option with this bag. I'm also a side sleeper, which makes a traditional bag harder to get along with.
I got the EE for warmer weather, and I found that I LOVED that it's a quilt. I can still cinch up the foot box & lower part of the bag if I need more heat, but it's so much more versatile in different situations. I'm seriously tempted to get a 10 or 20 deg quilt & sell the Zpacks just for that reason. I didn't have any problems with the quilt coming off, even when I had it fully open in "quilt mode". The other thing I really liked about the EE quilt is that I could un-cinch the foot box, but leave the lower part of it snapped closed to help hold it in place.