I struggled with Kubuntu as newbie (coming from Windows) - Mint was easier for me and I sticked with it (Cinnamon in my case, but my laptop is more powerful)
Your old stuff is most likely in x264 video codec, while, especially at the higher resolutions, x265 / HEVC and in rare cases AV1 are the standard today. But it also depends on the specific release how many streams (like audio tracks, subtitles) are included
That’s so stupid. If they made it like switching between warzone and multiplayer, that’d have been okay, although still unnecessary, but this just bad UX - again. Nobody believes their lie, that this is more than an update anyway, why pretend different?
Yeah, it will probably work out if all 1.4 billion people all drive alone in a car, occupying at least 15m² each. Needs one more lane, but then traffic will be solved!