Maintainer of the Swedish regional filter in uBlock Origin.
I use the binary provided by Mozilla at https://www.mozilla.org/en-US/firefox/
I even wrote an installation script that takes care of it all. (For amd64, not arm64. I’m not sure if they provide a stand-alone arm build.)
Linux Mint do not use the HWE kernel like Ubuntu. However, be on the lookout for a Linux Mint 21.2 Edge ISO. It’s not released yet, but that ISO will use a newer kernel.
Try with the invidious instances or piped instances that are the closest to you.
Sandbox your browser in a VM or something. Don’t use the same browser/VM for banking/personal stuff and everyday browsing. Most browsers will do. (Except Chrome/Edge/Opera/Yandex). Personally I prefer Firefox. LibreWolf can also be an option, but you have to opt-in to see videos with DRM etc. Tor is also an option, but the downsides are captchas and websites that block you.
If you’re even more extreme you can also use uBlock Origin in “hard mode” and the no script toggle. That will block JavaScript and prevent websites from connecting to any 3rd parties, anything from tracking servers to CDNs. That will definitely break websites, so you’ll have to know how to unbreak them, which can be quite the learning curve for some people.
Why not Chrome/Edge/Opera/Yandex you say? Chrome is owned by an advertising company. Edge tracks you plenty. Opera and Yandex comes from authoritarian states.
The different heights could be related to your custom font or theme. Does it happen on defaults?