You pick out some benchmark app then run that as-is. Don't tinker yet.
Save those numbers then end that suspect items and run it again to see if that program was the culprit.
There are no safe sites today save maybe Ninite. All can cause trouble. Far fetched you say? What if your PC was on the verge of failing or had a barely working heatsink fan. The stress of testing could cause a failure so for me to write it's OK is not OK.
As to checking for common unwanted software, why not Grif's list at:
I would like to check on the speed of my computer. How do I know how fast it is processing? I see ads to check your slow computer but do not know if they are safe. Can you recommend a safe site to have my computer checked for speed, unwanted software, etc.
also how can I tell what is running in the background that might be slowing down my computer?
Thanks for any help.