I prefer an inflatable pad due to it's compactness when deflated and rolled-up...definitely make sure you have the inflation bag that comes with many of the options out there...sure makes inflating it a better deal.
I've primarily used a NeoAir Xlite (r=4.2) for quite a few years...temps down into the mid/high teens at the lowest. My son got me a Nemo Insulated Tensor for Christmas a couple years ago (r=3.5) I like the Tensor a bunch...have used it into the low twenties/high teens so far with no noticeable chill at night (FYI...I'm a warm sleeper). Had an Exped XP-9 (down) for a few years, but gave it to my daughter for sheep hunts together with me...she sleeps colder, and that is a very warm pad (r=8.0)...she kept it!
All the aforementioned fit on the Helinox Lite cot just fine.