When comes to sleeping pads...
One thing to consider is whether you are dealing with a cold night here and there with warmer daytime highs or truly cold weather around the clock. The times and places I have toured had some cold overnight lows but it usually got to 50F or more in the daytime.

For that kind of conditions my uninsulated Neoair X-Lite (R2.3) has been fine since while it may get cold at night, the ground isn't frozen hard under me, even when the overnight lows got into the teens F. So even for February on the Southern Tier it was fine.

For real winter conditions with hard frozen ground I would add a foam pad along with the NeoAir. The thing is, I don't generally tour when/where those conditions are expected. I might need to add the foam pad on an XC ski trip or a winter backpacking trip, but have not felt the need to do so for touring.