Photoshop CC was the original version of Photoshop that came out after the CS versions were out. After the introduction of CC's, they started distinguishing versions by release year. 2020 is far more recent than CC
Use the latest version if it works well for you. You can delete the others, if 2020 work well. They just dropped the CC in the name. No real change other than a new version.
Older versions can be useful if you need a deprecated feature or plugin that's no longer supported. It's also good to have in the event that the upgrade doesn't work so well for you (it happens). The point is, you have choices.
So what I am seeing is I have old and new versions of Photoshop. It is odd that I still get updates for the CC version I started using, when I guess I should delete all but the newest Photoshop 2020 and get used to it.
>>>So what I am seeing is I have old and new versions of Photoshop.
A few years ago, Adobe used to remove old versions and leave you with just the newest version. That caused an outcry from people who were not ready to upgrade or needed older versions for old plug-ins and other reasons.
Now Adobe installs new versions side by side with older versions and leave it up to the user to decide when to uninstall older versions.