The main thing I like about containers is portability. Backup/copy your mounted folder with all the application’s data to any other system, point a new container of the same app to it and you’re up and running.
All the other advantages mentioned already are a really nice bonus.
Do you actually need hardware transcoding for your media is the real question. I haven’t bothered with 4K content so maybe that’s why but I’ve never used a GPU on any media server be it plex since the early days or jellyfin the past few years. Never ran into a situation where I couldn’t play a video file properly on any of my devices.
Are you trying to solve a problem with playback of video content or just want it for the sake of having it? If it’s the later I’d say to not bother especially if your budget is low. At some point you may actually need it at which point you can plan the hardware more appropriately.