Ah, so that bug affected Windows 10 too. Been playing with Windows 10 on both virtual machine and a real machine, no new bugs found when it comes to Drakan, except the usual bugs in virtual machine due to virtual graphics card being rather poor compared to the real thing. In multiplayer, the biggest issues are probably various errors in some player created levels, exploiting bugs in the game engine, making it crash.
I was unable to reproduce any sort of mouse problems, but definitely try running the game with dgVoodoo. Another thing that comes to mind, maybe you have some weird program running in the background.
As for Windows 10 in general, right now, it seems to lack polish and fluidity of Windows 8.1. There is still software out there that needs to be updated before it works properly with the new OS. And then we have the annoying new policy that all updates from Windows Update must be installed, including buggy drivers. They can be hidden, but no option in GUI, instead, separate app must be downloaded to get the functionality back. Or how about the annoying Xbox app that records games in the background, slowing them down, and can't even be turned off normally without signing into M$ account. Can be turned off via registry, or removed altogether with a PowerShell command, but still. And that's just some of the things, one can find a lot more bull**** when it comes to Windows 10.
"When a human being takes his life in depression, this is a natural death of spiritual causes. The modern barbarity of 'saving' the suicidal is based on a hair-raising misapprehension of the nature of existence." - Peter Wessel Zapffe