This is my packing list as an example.
Freezing cold will inhibit function or outright damage your water filter, fuel, and any devices with batteries, so it's important to wear these in a pocket during the day, and keep them in your sleeping bag at night.
The reason you would use a 35F bag for a 45F temperature, is that sleeping bag ratings are usually false, and you have to add 10 degrees to know what you actually need. Actually, you end up having to test the bag for yourself.
However, you can make due with a smaller sleeping bag, by wearing your clothes to sleep. A base layer is better preferred by the community over a sleeping bag liner.
They make some sleeping bags that you can wear walking around, but they fit loosely and it would be hard to do much in them besides sit in place.
I'm not a fan of quilts. The bottom of the sleeping bag does compress under you, but it also wraps around you rather than the sleeping pad, and the immediate places around the contact points are not compressed.