Major issues warnings from an EtreCheck scan on my Mac (Runaway process)

Activity involving the Photos app are still at play:

Top Processes Snapshot by CPU:

Process (count) CPU (Source - Location)

photoanalysisd 127.59 % (Apple)

Other processes 74.30 % (?)

EtreCheck 8.50 % (App Store)

photolibraryd 8.43 % (Apple)

cloudphotosd 6.55 % (Apple)

This article has some suggestions for dealing with that:

https://apple.stackexchange.com/questions/310594/what-is-photoanalysisd-and-why-is-it-using-77-of-my-cpu

Please post the full report. You can include it by using the "Additional Text" tool in the ASC editor. Be sure to enable "Full Disk Access" in order for EtreCheck to provide a complete report that will also include any app crashes and/or kernel panic reports.

In addition to what Tesserax said, you will also need to run Activity Monitor.

The Mac App Store version of EtreCheck cannot directly see processes owned by other users, such as the root user, on your computer. It just adds up all of the CPU usage that is not accounted for and calls it “other”.

What you can do instead is use Activity Monitor. By default Activity Monitor will behave the same was as EtreCheck, but you can change that default. In Activity Monitor, go to the “View" menu and make sure it is set to view “All processes”. Then you will have to leave Activity Monitor running and, ahem, monitor it.

Process usage will change frequently and heavy CPU usage can come and go. If you are looking at Activity Monitor at exactly the same time that EtreCheck looks at CPU usage, then you will be able to see exactly which processes EtreCheck is talking about.

Additionally, as Tesserax says, your full EtreCheck may contain additional diagnostic information. If this is a problem that has been going on for some time, the operating system may have already noticed it and will have created a CPU usage report that will show up in your EtreCheck report.

You will need “Full Drive Access” in EtreCheck to see this information. In EtreCheck, go to the “EtreCheck” menu and choose “Preferences”. Then, in the Preferences dialog, click on the “Privacy” tab. At the bottom of the window you will see a checkbox to “Allow full access to the startup drive”. Click that button and follow the prompts.

Another option would be to download and use EtreCheckPro instead. It is free just like EtreCheck. But because it is no in the Mac App Store, it can directly see all of these processes. Unfortunately, as I am the developer, I’m not allowed to give you a direct link for EtreCheckPro here in the forums.