I’ll throw in a second for Capilene 3. I used this for a base layer on my JMT thru-hike. For the most part, it was my sleep clothes with a couple of exceptions — cold nights and hiking up Mt. Whitney (we started up around midnight).
Most of the time for hiking, I wore shorts and a tech-tee. I’d add a wind shirt, then when it got chilly, a fleece.
The Capilene 3 worked really well for sleeping.
In the end, these decisions are highly individual. The best advice I can give you is to make your best educated purchase, but to field test before your thru-hike.