I'm having this issue too on my 6620g. Youtube is dropping frames like crazy and when I try to full screen a video is runs like a slideshow or even crashes. Netflix will crash entirely without even playing anything. I tried to play a game yesterday and it was dropping frames too as well as movies I have saved directly on my hard drive. The entire Windows 10 experience seems slow. I tried changing my video card driver to windows 8 version and it seemed to help a bit, but still no netflix or full screen on Youtube and it will crash a lot of my applications before it opens them. I would try reverting even further back to a windows 7 driver, but W10 is refusing to let me do that.
I get the feeling that AMD won't support this card anymore and this is never going to get any better. I was so excited for Windows 10, but I might have to revert back to windows 7 just to be able to use my laptop. I really can't afford 700 bucks for a new computer right now.