Upgrading RAM in 2020 iMac

First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

That being said you've installed on one the worst offenders at compromising system performance, MacKeeper. It's also a memory hog. Uninstall it according to the developer's instructions. Then you can check to see if you've removed all of the supporting files by downloading and running Find Any File to search for any files with the application's name  and the developer's name in the file name.  For MacKeeper software you'd do the following search(es): 

1 - Name contains mackeeper

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

Go to the Clean Up section of the report in Etrecheck and remove those orphaned files.

In the Diagnostics sections some apps have been crashing like FontValidator. Make sure you have the latest version, compatible with Big Sur, installed.

I also see that you have Snapz Pro X installed. Does it work for you in Big Sur? I had it several systems ago and it finally quit working around Mojave for me. Being 32 bit it wouldn't work with Catalina and beyond. I'm curious how you got it to work.

I've since migrated to Keyboard Maestro which I've found to be many times better than Snapz Pro every was.

Because MacKeeper is malware and will totally mess up your system. Please read below:

The best antivirus, cleaning app, and overall maintenance app for Mac OS is Mac OS itself. All you need to do with Mac OS to keep it secure and running well is to keep it up-to-date and do periodic (about 1x per week) restarts. Other than that, leave it alone. Adding third party antivirus, cleaning, security and other types of maintenance apps to Mac OS adds no additional level of security. The only thing these apps do is have the opposite affect users want. They make Mac OS slow, unstable, generate odd behavior (much like you are experiencing) and make Mac OS appear buggy. 

Please locate the developers uninstall instructions for MacKeeper and follow to the letter. Then restart in Safe Mode per the directions in Use safe mode to isolate issues with your Mac and then restart normally. 

Install memory in an iMac - Apple Support

Before adding more RAM you should see if there's any 3rd party software that might be causing the problem. So download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Additional Text button to include the report in your reply.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Then we can examine the report and see if we can determine what might be causing the problem.

Your RAM is installed incorrectly. Please put the original Apple RAM in slots 1 & 2 (Slot 1 is the top slot, slot 2 is right below it) and then install the upgraded RAM in slots 3 & 4. Please carefully review the screen shots of my 2020 27" iMacs RAM, pay attention to the slots used and the speed of the RAM.

It's running in the background and should be completely uninstalled. Of course it's you decision to make but non of the experienced contributors to these forums would have it on their machines.

KM is better because I have over 100 shortcuts/macros and can quickly search for one by entering any word or phrase in the text (if it's text insertion) or in the title I give it. With Snapz Pro I had a difficult time finding the macro I wanted to remember the keystrokes. And it works on menus, preferences, i.e. I can change Safari's text size with a simple key combination if I need to. Bottom line: with my aging eyes and failing memory it helps me remember the macros much easier.

I'm just surprised it's still working for you. When Catalina came around it had already died and I asked the developers if they were going to upgrade and go a noish answer.

It's best to use pairs.