Tool called ddwrapper helped, you only need to set NoVideoMemory to 1 in configuration file. You can find it in Google.
Current GOG version actually works fine with wine directdraw, but it has alt-tab problems and takes a long time to load. With this wrapper there seem to be no problems.
If anyone's still struggling with getting IwD2 to run fine on a Win10 system, this helped me.
What I've done was:
1. Installed the game from Gog.
2. Installed the Tweaks Anthology.
3. Installed the Widescreen mod (at this point the game would run fine but wouldn't alt-tab/minimise at all).
4. I downloaded ddwrapper and set NoVideoMemory to 1 in the config file, then moved both of these into the IwD2 installation folder.
The game seems to be running fine and I can alt-tab out of it, too :)