The rest of my Mac computer is completely slowed down when using Vivaldi, please help

[priestlyashes]

The kind of computer I have: iMac Retina 4K, 21.5-inch, 2017

Specs:
Processor: 3.6 GHz Quad Core Intel Core i7
Graphics: Raedon Pro 560 4 GB
Memory: 16 GB 2400 MHz DDR4
macOS: Ventura 13.7.1

First thing of note: the most recent Vivaldi update (as of 11/5/24) initially FAILED. I'm completely unsure why it failed, that's never happened before. But I was able to re-download it and install it successfully (I think). This is what it says:

Vivaldi: 7.0.3495.10 (Stable channel) (x86_64)
Revision 46177f82db4977c295fe8a3bdecb6a552df0838d
OS macOS Version 13.7.1 (Build 22H221)

Info: I use Vivaldi for personal and work tasks, with two separate profiles. I will be the first to admit - I have a lot of tabs. Like, a lot. It's a part of my work mainly. Other programs I have constantly running on my computer during the day include Slack, Firefox, and a calling app called JustCall (I work in a call center type environment). I sometimes use the iMessaging feature as well on my Mac. I do have a secondary screen set up that I use.

Issue: When I'm working within my Work profile Vivaldi window - everything runs smoothly and like normal. I am usually streaming a video on my second screen (this is what I use Firefox for) and it runs smoothly. As soon as I click outside of my Work profile Vivaldi window to do other things, such as using Slack, my JustCall dialer, my Firefox window, messaging, etc., everything lags. Including the second screen where I am streaming a video, it will lag (not the audio, but the video). I'd say it's probably lagging 1-3 seconds behind the actual action I perform. This even occurs when I try to open up my personal profile in a separate Vivaldi window. As soon as I get back into my Work profile Vivaldi window, everything is running smoothly again.

What I've done so far:

• Cleared all cookies.

• Cleared history and ensured it's only saving history from a week or less ago.

• Hibernated all background tabs in all of my workspaces. Changed settings to automatically hibernate inactive tabs.

• Removed all extensions I don't use. I now have only three, OnePassword, a Translation extension, and one for allowing me to work in Google Docs offline.

• I went into my privacy settings and changed it from blocking all ads and trackers to just blocking trackers. I do have it set to block all cookies, and am utilizing all of the other security features like asking websites not to track. This is important to me, so I'd like to keep these settings if possible.

• Completely exited and restarted Vivaldi browser.

• Restarted my computer. Shut down my computer, left it over the weekend to rest, then opened it back up Monday and same issue.

Some things I noticed: I used to have a similar-ish issue with Google Chrome and with Opera, which is what caused me to seek other browsers. Eventually they would slow way down. I've noticed that all of these Google-based browsers use a crapload of Renderers that fill up my Activity Monitor. Perhaps this could be part of the issue, but I've been using Vivaldi for several months now, and haven't had this problem until recently. I'd say it started last week.

I've Googled this and tried all of it's suggestions. I even went into my computer's files and cleared out a lot of crap and emptied the trash. I'm at a loss. If anyone knows how I can fix this, please help!