Solid advice.I advise against CCleaner unless I trust the user to know what can be cleaned and what not, and especially, when.
Windows is not bothered anymore by idle files, at most, eventually, a drive may be fuller than it needs be due to some developers keeping installers in temp folders. This only is an issue if a few dozen gigabytes are used.
This is what I meanExcuse my ignorance, but what do you mean by set the cpu cores to the same speed? I thought cpu cores all run at the same speed. https://www.howtogeek.com/316572/why-do-cpu-cores-all-have-the-same-speed-instead-of-different-ones/
Do you mean enabling all the cpu cores? (Usually only 1 is enabled when first installing windows 10).