And for those playing along at home, the Plasma install was actually at partition nvme0n1p3, the bootloader at nvme0n1p1 from above. Everything else from the boot rescue page worked as anticipated, but the descriptions...
Plasma does seem to have a couple more display options using the Nvidia software under the advanced settings (can't remember accessing those under Budgie though), but not quite what I was looking for. But the file manager is waaayy more adaptive (I can live with this). Although now I am getting random display glitches no matter which driver I use (will look into forcing refresh rates later. Happy for now I just got the install to stick).
The overscanning "issue" actually isn't (had reason to bother sorting through the display options sans remote, and "clearscan" was turned off globally. There are just different presets on the tv for "movie" and "sports" and the like, and it is just a matter of cycling through enough of them to where the native display will fit.
All of the other weirdnesses, from the disappearing purple login prompt to the linux bootloader actually coming up as ufei (insert disk) are still there though.
And wow! Plasma sure isn't lacking for granularity. Maybe not the clean holistic approach of Budgie, but I like having the options.
A part of me is wondering though if the "A sophisticated desktop experience for the tinkerers" description doesn't have such an oblique install procedure just to be sure 😛
