Is this sleeping pad combo sufficiently warm for a PCT thru hike?

I woke up with ice on my bag several mornings in socal and the Sierra routinely got down to about freezing (I camped high) so I would want a pad comfortable to about freezing. For me, that was a zrest (2.2r or so) which I swapped for a ridgerest deluxe (3.6r I think) for the Sierra.

I would strongly suggest trying your air pad down to freezing temps. You can probably find camping on the coast or in eastern WA that would approximate those temps. Try it out and see what R value you need at those temps.

I wouldn't use an inflatable pad in socal, but that is just me. Plenty of people got away with it.

I use an inflatable and ~stack that with one or two thinlight pads by Gossamer Gear. You can get these pads in different thicknesses, but even the 1/8" thickness layered on top of an inflatable helps out the r-rating in a way that I feel. If it's really cold I'll put a 1/8" pad below the inflatable and a 1/4" pad on top of it; then you can mail home one or both pads when no longer needed.

As a bonus, in the first 700 miles or so there are more than average pokey things on the ground, so put the thin ccf pad under the inflatable on nights when you don't need the extra warmth.

Starting the AT early I used a standard neo-air and the two thinlight combo down into the teens and was okay with that. Unlikely you'll get that cold on the PCT anywhere.

I used a only a Z-lite for the entire PCT. Admittedly, I had a few cold nights, but I was okay with that.

The Z-lite Sol has a higher R value than the version I used. So, that, along with your Big Agnes Pad, should be more than enough for the Sierra. Brian's suggestion of using a thinlight instead sounds good to me. But you should test out your sleep system ahead of time if you're concerned about being warm enough.