While Librewolf does have its advantages, I find it hard to recommend over regular Firefox, at least for most people. Librewolf disables some features like WebGL due to security and privacy concerns.
I haven't watched the video yet, but keep in mind "resource usage" being lower isn't always better.
For example, Plasma had an issue for some people where animations would not happen, freeze the system momentarily, and stutter. The reason why turned out that these people were using slow drives. Plasma was trying to load the bytecode for the QML animations from disk, but the IO operation took too long so the animation suffered. Had this bytecode been stored in memory, the performance would have been better.
But I also don't want to discount the fact that some (perhaps most) of the time, high resource usage is a bad thing caused by poor programming and using technologies that are heavier, like Electron. Whether those tradeoffs are worth it are another matter.
I wish more developers actually used their software low-end devices to find performance issues. I recently got an Intel N100 and it's actually been a decent experience on Linux, though Gnome shell's animations are a bit stuttery even on Gnome 48. Haven't tested any other desktop though.
One thing that bites me about Loupe / Image Viewer is that it always goes through images in alphabetical order, despite the sort option you have set in nautilus.
Sushi does go through items using the same sort option set in nautilus.
Though it can be finicky with videos, so I don’t use it for that.
AirPods work great on Android. Just make sure you have them configured how you want (like the touch and squeeze actions) because you can’t change them.
An alternative to AirDrop is LocalSend, but it has a massive asterisk: you must be on the same WiFi network. But I think you can start a hotspot on your phone and connect your other device to that and it should work.
Other than that, I’m not sure I’m qualified to answer for other stuff. In general I stick to cross platform apps and in general find continuity features more annoying than helpful.
Adding non-Steam games has never worked well for me.
Another issue is that there is a database of tweaks Proton uses to make games work better, but I don’t think it uses it for non-Steam games.
Heroic with umu do use these tweaks.