Quilts and bags with no insulation on the bottom are good if you sleep on you back and don't move at night. But if you rollover or sleep on your side they can have cold spots and let cold air in. Also no hood makes them feel colder than a bag with one
I can't sleep on my back at all, but I use a pair of quilts to hike all year. Drafts are a problem if you don't keep the edges down or flop around too quickly/recklessly, but drafts can be a problem in sleeping bags too if you flop around. The only time I use a sleeping bag is when I'm car camping and the weight and bulk of my synthetic sleeping bag isn't an issue.
Of course you have to wear something on your head. Most of the year I use a Rayway bomber hat. It's synthetic, so I can wear it and sweat in it a little while hiking. When it's going to drop into the low 20's °F for many night or much lower for any time, I'll bring a down balaclava. I find like better than a hooded sleeping bag because I can turn around without putting my face into a hood or getting the zipper "lost".