Someone asked me to peek in here briefly. Yea in this case it was the GPU. Encoding is fine because there's no complaint in the log about that, and I mean xeons with 32 logical cores so encoding is not going to be the problem.
For Unknown Richard:
Hey there, I am aware of things. I'm always watching and talking with the community, and people always reach out to me if there's anything unusual going on, especially if it affects a lot of people. I have seen your thread and I actually really appreciate all the logs and comparisons; I wish more people would do that. I apologize if I don't always respond though -- I'll respond here just to let you know I do see things.
Windows 10 does seem to make a bit more significant use of the GPU than previous versions, so that may be a factor -- but I'm not entirely sure because only microsoft knows all of the changes under the hood. I can only make a judgment based upon what I see from users and what I see/feel myself. Kind of sucks that we have to be in that position but that's just the nature of the situation. It seems microsoft has changed the way it handles compositing a bit though. It feels like the windows 10 anniversary update in particular has further changed the graphics backend on windows as well (especially considering the driver issue we've been having if that's any indication that microsoft has changed things). How much microsoft has changed things I'm not sure, but I can't really do much if it's an operating system issue or a change in operating system design.
What can be done? Well, in your case I'd sadly just have to recommend a GPU upgrade. You're doing 1080p 60fps so you have to keep in mind that's pretty demanding as it is. You still using that 750 ti? Definitely upgrade if/when you can afford it. I think the only thing you can do is either stick with 8.1 or upgrade that GPU. In terms of the code, if I thought there was something off, something incompatible, or something I could work around, I would change it immediately to help (like I ended up doing with the driver issue), but in this case I think that the operating system has just become a bit more demanding, and to compensate you may just need to increase your system's horsepower a bit to compensate.
Just my opinion on the matter though. Just remember that I am always monitoring things, even if I'm not always in threads responding. This program is my life pretty much at this point, so the health of the program is my own health