
Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.

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R Value is cumulative so having 2 stacked pads will increase the total insulation. With that 2.2 + 4.x you'd be in the range you'd want to be for those temps. I use an Exped Dura 8 which is 3.5in thick (8.89cm) and works well for backpacking. When car camping I use a Deep Sleep (R9) that is 3in thick (7.62cm). Since both pads in question are about the same insulation value, I'd lean towards the thicker as long as it doesn't compromise your pack size or weight.
Was sleeping in 26 degree weather this past weekend. I used seatosummit camp plus pad 4.3r and a klymit 0 degree bag. I woke up like at 3am sweaty.
I have a Sea to Summit Camp Plus long and it's extremely comfortable but it's packed size is not small whatsoever. It takes up a lot of room. I have been recommended the Big Agnes Rapide SL insulated several times now. Little over a 4R value so plenty warm for 3 seasons or possibly even 4 if you have a good bag. Another option is the Sea to Summit Ether light XR Pro insulated if you need a warm pad. That one has a rating over 7.4 R value and it packs down dang small for what it is.
I'd go sleeping bag or pad. What model of each depends on the type of camping you intend on doing. If you're going straight car camping, highly recommend the REI Siesta 20 hooded bag. I absolutely love mine. For backpacking, you'll want something down filled most likely and I've heard good things about the REI magma and of course, the Nemo Disco is pretty much legendary at this point. For sleeping pad, I've tried a few and really like the Big Agnes Rapide SL insulated. Again, if you're car camping, the Sea to Summit Camp Plus Si is another great option that's a bit cheaper (80ish on Amazon) and great for side sleepers as it has some foam in it. StS also does their pillow lock system which is really nice for keeping your pillow in place at night. Does not pack down very small though. Thermarest is another really solid brand for sleeping pads as you probably know, but I've found them to be among the noisiest. I have yet to find a better inflatable pillow than the Nemo Fillo. Packs down very small but uses an inch thick memory foam layer in top so you aren't getting that squeaky inflatable sound in your ears all night. Those are 50 at REI. Once or twice a year, Garmin does a sale on Inreach devices. If wait to pick one up then unless you know you'll be out of cell service a lot in the near future. The Inreach Messenger is excellent, especially if you already have a Garmin watch and don't need the additional mapping capabilities of the Inreach Mini 2/3.
When I started out on this, I kept seeing suggestions for 3-4" memory foam toppers or such and cutting it to size, so that's what I did. I ended up ditching it, so that was a big waste of money. It wasn't thick enough for one, moisture issues concerned me as well. So I bought Sea to Summit Camp Plus Self-Inflating Foam Sleeping Mat for about $80 which wasn't much more than what I paid for the foam topper and it's been soo much better. It's a hybrid foam/air mattress, so the issues of the foam are limited by being inside the air mattress, and I can get more support in less space by putting air in the thing. The one maintenance thing I have to keep up on with this is that it says you should remove the plug and let the air out if it's going to be in an area where temp changes drastically, like a car. Essentially as the temp gets warmer, the air inside the sleeping mat expands and can rupture it or separate the foam from the liner which would compromise the structure of the mat and likely be uncomfortable to use. So in the morning as part of my routine I just take out the plug so air can just flow out, then fill it up again at night.
I recently got the Sea to summit camp plus self inflating sleeping mat. After camping with it i've realised it is way too big when it's in my pack. R value is 4.3 and it's really warm but i don't think it's worth how big it is when it's packed away, plus i rolled off the sides twice. Any recommendations for a new one with similar R value and packs a lot smaller? I've been looking at the Big Agnes Rapide SL but seen mixed reviews about mainly surrounding the fact that it's probably not actually R4.8 because it sleeps pretty cold
https://www.rei.com/product/135417/sea-to-summit-ultralight-air-sleeping-pad?sku=1354170002&store=&CAWELAID=120217890004806433&CAGPSPN=pla&CAAGID=147758271319&CATCI=pla-2077566611927&cm_mmc=PLA_Google%7C21700000001700551_1354170002%7C2077566611927%7Cbrand_flag%7C9920629669&gclsrc=aw.ds&gad_source=1&gad_campaignid=9920629669&gclid=CjwKCAjwg7PDBhBxEiwAf1CVu1fAbcZ3QQVWH-mwf-AhewUlIW05eSDZS31n8v4YuCkqF1QmiNAjpBoC9q0QAvD_BwE Or this slightly heavier one for $100-$109 https://www.rei.com/product/199005/sea-to-summit-camp-plus-self-inflating-sleeping-pad-mummy

Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.

Exped
Ultra Series
Lightweight side-sleeper comfort, but a bit pricey and bulky.

NEMO
Tensor Series
Ultralight side-sleeper comfort, but slippery and prone to leaks.

Big Agnes
Rapide SL Insulated Sleeping Pad
Comfortable with side rails, but heavy and warmth claims disputed.

Therm-a-Rest
NeoLoft™ Sleeping Pad
Very comfortable, good service, but heavy and bulky for backpacking.

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Therm-a-Rest - NeoAir Xtherm Series