We don't have a spy that's for sure!
That's correct!
Neon unstable/testing already contains the relevant branches. Neon user edition should receive it as normal when it releases. When Neon will update its Ubuntnu base is a question for Neon developers.
Relaxed at the moment :)
It has not been developed in the last few years but always krunner! A recent-ish feature that was already in Plasma 5 is to bind key presses to your extra mouse buttons or tablet tool buttons
I think everyone has different preferences on how they use their machine. However I would invite to just try Plasma out. One thing where it stands out is in my opinion that you can tailor it to your wishes and use case.
It may be not user visible and technically not a Plasma but Qt change but I find the work so that apps survive the compositor restarting amazing. See http://blog.davidedmundson.co.uk/blog/qt6_wayland_robustness/
That's an amazing idea! Currently I am using my laptop next to my desktop screens as a sudo webcam :D