MacBook Pro big-sur freezes with vertical script lines and overheats

While some apps which use GPU hardware acceleration can get some graphical anomalies, those anomalies are usually restricted to that particular app. Your picture shows the issue is occurring outside of the Teams app so that would tend to tell me Teams is not likely to be responsible especially when you say you have the issue with other apps.

When you performed the clean install of macOS did you thoroughly test the laptop before restoring or migrating from a backup and before installing any third party apps? If the issues don't occur with a clean install, then begin installing your most critical apps one at a time making sure to thoroughly test them so you can easily locate which app may be the source of the problem especially apps which install drivers.

If you suspect Big Sur is the problem, then perform a clean install of the original OS that shipped with the laptop from the factory.

If you can prove the issue occurs on just a clean install, then it means you most likely have a hardware issue making it easier for Apple to decide to replace the Logic Board in the laptop. Judging by your picture I believe you have a bad Logic Board, but convincing Apple to perform the repair can sometimes be a slow time consuming process if the issue does not occur with a clean install.

When testing intermittent issues I like to stress test particular aspects of the system to try to narrow down the issue and make it more reproducible, but unfortunately Apple doesn't really care for third party apps for troubleshooting and I can understand why to some extent, but it also shows that Apple doesn't know much about troubleshooting odd & intermittent issues. Sometimes you may find a tech working for an AASP will be more open and knowledgeable about general hardware troubleshooting.

I personally like to use "mprime" (aka Prime95) to stress the CPU, memory, cooling system, and power supply (they have a "Torture Test" mode which Windows PC builders have used for years to make sure their custom built and overclocked PCs are stable and healthy). I also use "gputest" (only runs from the command line with recent versions of macOS) and the Unigine Benchmark Demos (Valley or Heaven) to test the GPU, while I use Memtet86 to test the system memory. I've never seen these apps have any issues when run on good healthy hardware, but they can reveal hardware issues in a more easily repeatable manner if the hardware is bad. It helps me to confirm I've replaced the correct part when I'm not sure which one is responsible especially when using a known good clean OS. I've even download several HD movie trailers and run several of them at the same time on screen to help stress the system and find issues. Being able to reproduce the issue on demand is important to a real repair tech (Apple doesn't usually have real repair techs that understand the lower level details although I'm sure there are some exceptions especially at an AASP).

If the Apple Diagnostics reports a hardware issue, then make sure to take a picture of the error so you can show Apple.

Make sure to disconnect all external devices especially when you encounter the issue to make sure an external device isn't somehow contributing to the issue (especially if Apple is unable to reproduce the issue).

I wish you luck since Apple is much more difficult to deal with today than they were 10+ more years ago.

The thing that stands out to me is why you migrated from a 2013 system and then later intending to restore from a backup. You should have just restored from the backup of your system. This makes me suspect a possible software issue with your current problem.

It was good that you decided to first upgrade to Big Sur before migrating from your backup since you should first upgrade macOS to the same version of macOS you had before the laptop was repaired so that the system firmware is updated to the proper version. If you don't install the newer version of macOS, then your system will retain older outdated system firmware which could be a security issue or could possibly cause other problems since macOS won't be expecting this situation.

Like I mentioned in my previous post the only way to be sure whether you have a hardware or software issue is by testing with a clean install before migrating or restoring from a backup and before installing any third party apps. If this works, then you can restore from a backup since the backup is likely Ok. If you only encounter issues after restoring from the backup, then perhaps you have a software issue so you could try restoring from an earlier backup where you know for sure had no issues.

Diagnostics rarely find & identify hardware issues. They are just one tool a good tech uses for diagnosing a system. Unfortunately Apple only trains their techs to use the official diagnostics and to test with a clean install of macOS. This is why so many people end up being unhappy with Apple support. These USB-C Macs and the more recent versions of macOS from 10.13+ make this process even more difficult, because the new hardware & OS have so many crazy weird idiosyncrasies. I absolutely hate the USB-C Macs and recent versions of macOS for these reasons.

Keep in mind a good tech will use whatever third party software or devices is necessary to try to identify a failure of some sort. Even then some issues can be really hard and time consuming to identify with any degree of certainty. Some issues require a lot of time and ingenuity of the tech to try to find some type (any type) of failure or slightly odd system behavior. I even used to use a Linux OS boot disk to help identify hardware issues, but unfortunately with newer Macs this no longer works because macOS leverages certain aspects of the hardware differently than Linux does due to those previously mentioned idiosyncrasies.

You are more likely to find a more knowledgeable and well rounded tech at an AASP, but unfortunately many AASPs only blindly follow Apple's official guidance which I've already shown is quite limiting. For Apple it is all about speed and flashiness. That little MRI report they like to show off to indicate the Mac is healthy is from a "diagnostic" that runs for only a few minutes and mostly indicates that the various components & sensors are physically present. The only "real" test it performs is a very quick memory test. Keep in mind that I've personally run diagnostics on systems for several days non-stop before some issues begin to show up. Apple does have some better service diagnostics that take a couple hours to run, but even then those diagnostics are not made to be run more than once much less for a day or two.

As for your concern about having Catalina installed when Apple returned the laptop. The reason for this is that Apple images the SSD on the replacement Logic Board with the OS that originally shipped from the factory. You should always first upgrade macOS to the same version you had before getting the laptop repaired so your system has the proper and expected system firmware so that your backups work properly.

You can provide Apple with product feedback here, but keep in mind they will not get back to you:

https://www.apple.com/feedback/

You can also call or write to Apple corporate to show your displeasure with the Apple experience.

https://www.apple.com/contact/