Well air is a great insulator and having an xl means you are on air and not touching the ground when asleep. It packs to the size of a 1l nalgene water bottle. Probably a little longer but not much. Very compact for the size and comfort.

Not that I want to discuss it, but only air that isn't moving is a (somewhat) good insulator. That's why people don't sleep directly on uninsulated cots when it's cold, and that the hammock guys have had to come up with under-hammock down duvets.

I carry two Thermorest pads, when there are two of us I cover the entire tent floor! when there is just me, I double them up. They are light and fit my kit well

Big Agnes also makes a half length aircore and I own both. The half length cuts off just below the knees. It supports just what's needed to be supported and packs 1/2 smaller than the regular aircore. About the size of a can of soda. And since you camp in warm areas, also purchase the Big Agnes Nampa bag. It packs down to the size of a gatoraide bottle and will keep you warm to 40F.