we have an outwell creek double bag, nice and warm with plenty of room and you can unzip it to make 2 bags or unzip it to have a loose top when its a little bit warm.
Yes but with the Nitestar XL bags they are so big you dont notice & the flaps cover them well so no cold surprises.
We rarely zip the top of ours up they are so snug & because of the size they fall round you like a blanket.