OK, so I should point out a few things about the desktop compositing issue with Windows 10:
1. Not EVERYONE is suffering from it. There's a whole slew of factors involved and it's not clear what those factors even are, as two people with nearly identical setups can end up with one person having issues and the other not.
2. You can't rely on framerate tickers to find the problem since the frames are being rendered, the compositor just isn't painting them, so you need to see it with your eyes, and quite frankly, some people THINK they can see 60 FPS, but in reality, they can only tell if something is higher than 30 FPS and they don't actually discern high enough to tell if something is actually 60 or somewhere between 30 and 60. (I've tested this myself back with my old 120 Hz CRT monitor and I lose my ability to distinguish framerates around 80 to 90 Hz.)
3. How a program functions internally is a big factor. Some programs have constant stuttering, some programs will stutter a little sometimes but other times be fine, while some programs will be fine for minutes on end and will then just magically start stuttering for awhile before going back to normal, but ALL OF THIS goes away the minute you run one of these programs in an exclusive full screen mode.
With DOSBox in particular, it's only noticeable for me for games running higher than 35 FPS, and this seems to be about typical for me as I run DOSBox in OpenGL mode so that I can get a well resized window without aliasing, but I'm finding the compositor is getting confused with triple-buffered OpenGL stuff, rendering only two out of every three frames when not running exclusive full-screen. Unfortunately, nVidia's settings related to this only affect whether triple-buffering is ENFORCED with OpenGL, not if it's used at all. So you can either force it on, or not force it on, meaning it might still do triple-buffering anyways.
However, this problem still affects DirectDraw or Direct3D games too, just in different ways, so using those modes in DOSBox or any of the branches I tried (X and ECE) doesn't help either. :/
BTW: Back when I was first trying to complain to Microsoft and nVidia about this I recorded a video demonstrating this weirdness by pointing my 60 Hz camera at my computer screen while OBS captured Minecraft footage, and the video clearly demonstrates the OBS window showing a HIGHER FRAMERATE THAN THE GAME ITSELF. o_O
Here's the 50 MB MP4 file on my website for your downloading and viewing perusal: http://www.pixelships.com/files/fpswoes.mp4
--- Kris Asick (Gemini)
--- Pixelmusement Website: www.pixelships.com
--- Ancient DOS Games Webshow: www.pixelships.com/adg