I expect CM5 to be cooler and faster than CM4 due to just being a generation or two ahead in node process. Basically, an undervolted/underclocked version would certainly run cooler even under full load, and still be overwhelmingly faster. A stock clocked version would throttle if pushed to limit without proper cooling, as many intel CPUs in fanless design do (like, 10 seconds burst then throttle down).
I wouldn’t use my mobile device as any kind battery powered mining rig or an LLM training infrastructure anyways, so I’d overclock the CM5 inside uConsole and enjoy.