Windows 10 running Darktable not using PC at full capacity

Yes that is a known behaviour:

following the link you will get the info where the log output is written to:

I read a lot of information in the manual to turn on some debug settings, but I cannot see any debug information. Where can I find those debug logs?

The Windows version of dt by default logs its debug information to the following places:

Windows 10: C:\Users\[username]\AppData\Local\Microsoft\Windows\INetCache\darktable\darktable-log.txt