Pokemon is a 30 fps game so citra will report 100% speed as 30 fps (even though its outputting 60 fps because citra will output a duplicate frame)
Yes you can trust those numbers on the bottom bar; they are accurate.
the fps in pokemon sun moon are drastically lower outdoors compared to indoors.
that means your cpu has 8 cores (in your case 4 cores and 4 virtual cores) and citra is maxing out one core. considering citra currently only uses one core, its pretty standard. and before you ask "why isn't it multithreaded" you should realize that multithreading is really complicated and tends to be a major headache for anyone contributing in the future. Theres many more things that can be done to speed up citra before we reach to make it multithreaded. (and it already is multi threaded, but not in any way that would speed games up)
you don't have to liquid cool to overclock. you are usually safe to bump the clock speed up a bit on aftermarket fans, but thats besides the point.
My suggestion is don't bother overclocking and just wait for further improvements to the emulator. theres still things that can be offloaded to the gpu and plenty of optimizations that can be done. give it time.