Thanks for your elaborate notes! This is helpful information.
When I tried your commands, on Arch via libcgroup-git, `cgcreate -g cpu:cpulimit` only results in `cgcreate: can't create cgroup cpulimit: Cgroup, requested group parameter does not exist`, for some reason. But this is not a support ticket, I have not researched this at all yet. But cgroups only limit some processes anyway, never the entire core(s) - so it seems one could also simply use cpulimit [1] instead which emulates by sending SIGSTOP and SIGCONT.
About cooling_deviceN: While this does limit cpu functionality, this seems to only also set `scaling_max_freq` to an appropriate value, throttling because the fans are disabled. Not more useful than setting the frequency manually I presume.