Maxed out 2019 MBP 16" lag

Hello,

I recently noticed that my 2019 MacBook Pro (2.4gHz, 64GB DDR4, 8TB) started lagging even if no apps are opened. I have no apps in "Login items", but I have 1Password, Adobe Creative Cloud and Backblaze booting up with the system, which I have for many years. Sometimes it works smoothly, sometimes it lags when I edit photos in Lightroom Classic or Photoshop, and sometimes Final Cut is completely unusable to the point that I cannot do anything but either leave it for who-knows-how-long, or Force Quit and restart the machine. Even after restart, I have to wait for the kernel_task to calm down, because sometimes it goes up to 1000%. Sometimes it lags even when watching YouTube video or playing a movie. Then I go to check the Activity Monitor and sometimes I can't see anything unusual. Memory pressure is low, lots of free memory, CPU Idle has some room, CPU temperature is fine, and it's still impossible to work anything because of the lag. So, I don't know exactly what's happening, but sometimes everything looks fine, and sometimes processes are obviously high like kernel_task, WindowServer, and whatever high-demanding app that I'm using at the time.

I run all the latest software updates, including Monterey 12.1, which I updated few days ago, but I noticed this problem even on the previous version of Monterey.

I spent last two days trying to optimize my Mac. I tried all common advices like close all apps, remove login items, reset PRAM/NVRAM/SMC etc.. you can find all these things on many blogs and they repeat pretty much everywhere. I did all that, but nothing helped.

Also, maybe worth to mention few more things:

• My 8TB SSD still has around 2TB free space, so I guess that shouldn't be an issue either.
• I don't have many apps and I don't install anything other than what I need for my work. These are all from the reputable companies.
• Even when I install something and remove it, I try to remove all the files from Libraries completely, so there are no leftovers.
• I was hesitating for the long time, but I tried Clean My Mac and even it couldn't find anything significant to clean, because I do the maintenance on a regular basis myself.
• CPU temperature vary from 45 C to 85 C, which is fine too.
• I checked hardware diagnostics and there were no issues found.

Now, because I use my computer for photography and video editing, I need this to run smoothly, and I'm seriously considering new maxed out M1 Max computer, but before I throw another $7000, I'd like to see if there's anything I can do with this machine. This is great computer, only 2 years old and at the time it was the best you can buy. Yeah, it's Intel, but this lag, out of nowhere while watching YouTube and having one or two tabs open, shouldn't happen. And it didn't happen. I used this machine for two years and it worked fine.