not_admin I think whether it's 'worth it' on Q3 is very subjective, you need to try for yourself. Video quality will not be 5 times better on Q3 just because of 5 times more data, it will probably appear a little better at best. Noticeable, but not a game changer. On other headsets with better displays, the difference in quality between the two versions seems to be more pronounced.
I'm quite sure 8K Max that you can download is the same as 8K for streaming, at least they will look the same (when both are played in DeoVR).