So I have a TinySA Ultra, and I saw on a YT video that you should measure your antenna’s resonance to be sure it is working at 915 MHz. Can I use this spectrum analyzer to do that? Searches aren’t yielding much with ‘resonance’ + ‘TinySA Ultra’ keywords. The video I saw used a Nano VNA but I’m new and not sure if that is similar. Thanks much!
NanoVNA is similar in some ways, but performs a different function. It is what you need for antenna work. An SA is useful, but not so much for antenna tuning.
Plenty of YouTube videos on both products. I’d suggest you have a look at a few.
No, a spectrum analyzer historically doesn’t have that capability. There might be some products that have both features but generally speaking they are different tools.
The other tool that is good to have is SWR meter. It can’t give you data that a VNA can but generally speaking a low SWR reading usually means your coax and antenna is operating correctly.
Thanks for the great explanations - still learning 
much appreciated