These figures are very plausible. Most Linux distros are terribly inefficient by default.

Linux can actually meet or even exceed Window's power efficiently, at least at some tasks, but it takes a lot of work to get there. I'd start with powertop and TLP.

As usual, the Arch wiki is a good place to find more information: https://wiki.archlinux.org/title/Power_management

My CPU is at over 5GHz, 1% load and 70C at the moment. That's in a "power-saving mode".

If nothing would be wrong, it'd be at something like 1.5GHz with most of the cores unpowered.