I recorded the video at QHD (4k) and it appears that google+ doesn't use all the video quality. https://youtu.be/557jDNW4cRs youtube does. You can go into settings, and I see lots of HD settings.
I am pretty stoked that the phone has a QHD (4k) screen and can play the videos. I can see rain drops on the trees 10 feet away sharp as can be on the screen. Tiny on the screen, but they are there!