In Windows 7 64-bit (but not XP 32-bit), I could watch 1080P60 MKVs of HD-DVD rips (I owned the BR version, but didn't have a BR drive at the time), the AMD 780G IGP could play them basically flawlessly.
Note that the 760G may have had some of the video playback hardware disabled.
I had a friend that had a 780G mobo as well, but his HW acceleration wouldn't work for Twitch.tv streams at the time. It would play back fluidly, but it would have all kinds of bad macroblocks showing up in the video stream. That was using Flash Player, a while ago. (Years.)
I hooked him up with a low-powered GT610 card, and that has performed admirably up to 1080P60 H264 for him. I have no idea if he watches H265 or VP9 videos. I know that his internet currently doesn't really support 1080P YouTube all that well.