Exped - DeepSleep -5°C / 20°F

For 1 set for four season you’re gonna be comfy in winter but hot as balls in summer in most temperature ranges. That being said, you won’t die in summer with winter gear, can’t say the same in reverse. What sorts of temp ranges are you expecting to experience? That will give us an idea of what to recommend. Ignoring snow load where you would absolutely need a winter tent, I’ve used my basic 3 season tent in winter without issues down to about 25F. It’s your sleep system that keeps you warm. I had an Exped DeepSleep and a 10 deg REI sleeping bag. Wore simple undershirt and long-John’s and slept fine, face got a little cold but expected. This was car camping though so that pad would be too heavy and bulky for backpacking. Currently have an older Klymit that I used in Texas but haven’t gotten anything for lower SoCal temps yet but eyeballing Exped Dura, probably an 8 if I can find one at a good price.