The GMA 950 was almost obsolete when it launched, being a faster derivative of the GMA 900. It doesn't even support DX9c in hardware.
I'd go so so far as to say a DX11 capable GPU is a requirement for a good experience on 10. Doesn't have to be more then a HD2500. Win10 driver support for pre-DX11 GPUs is... spotty... at best. Like even Sandy Bridges IGP loosing all OpenGL functionality, unless you, ahm, force install the 7 driver.
PCI is only capable of 133MB/s on a good day down hill, so anything requiring even moderate bandwidth is going to choke.
GMA 950 (and I think other derivatives, like GMA 3100) is really horrible on Windows 10 (on 7 it's just very bad, but doesn't have this problem to this extent, and you can eliminate the dwm.exe hit by disabling Aero), even with drivers installed you can get almost 1 core fully loaded with just dwm.exe if you are watching a video on the web browser, because of how much work is being done by the CPU
I think it might be related to being WDDM 1.0 driver? I haven't tested other WDDM 1.0 cards recently; or maybe because yes, it's not even a proper DX9 GPU.
from what I was reading WDDM 1.1 makes a significant difference for the desktop windows manager.
GMA 4500 which uses WDDM 1.1 and has DX10 support seems to handle things a lot better with not so high CPU usage like with the GMA4500 I saw 5% usage by dwm.exe in a situation GMA 950 uses around 30-40%.
in any case, the 8400GS works ok with Win10 and uses WDDM 1.2 drivers, it seems to accelerate stuff properly, while something like the GMA 950 doesn't.
my Radeon HD 4670 (uses WDDM 1.1 drivers) also works OK in terms of basic performance on Windows 10, but the Geforce 8 works clearly better overall with driver compatibility and video acceleration, I know there are HD 4350 and such with PCI interface, but I think the Nvidia PCI (series 8 and higher) ones are better to use with Windows 10 because of the drivers, with windows 7 and lower maybe it's different
the max bus usage I was able to see my PCI 8400GS use was around 103MB/s, it's fairly easy to max the interface as I said just scrolling a web page... but I was also surprised as to how often it doesn't,
but I'll take the bandwidth starved 8400GS PCI over a GMA 950 anyday for Windows 10 at least, against most other things, not really.