I've found the compromise.
ddraw.dll from hires patch doesn't provide libwine/wined3d levels of performance, but it doesn't cause any slowdowns nor any other serious performance issues like gog version of ddraw.dll. It has some minor stuttering but I think I will stick with it, since it allows me to alt+click while sustaining an ok performance.
Just to sum it up for people who might come across this thread in future:
1. GoG version of ddraw.dll - terrible performance (slowdowns, long loading times, mouse lags in dialogues)
2. ddraw.dll from hires patch (
http://ton-hur.mbnet.fi/files/Arcanum/HighRes1.5.zip ) - gives you an ok performance (no slowdowns, much faster loading times, no mouse lags in dialogues, no lags when transfering multiple items between containers, etc). There are some minor stutters when scrolling the map though.
3. ddraw.dll (with libwine.dll and wined3d.dll (
http://bitpatch.com/ie_ddrawfix.html )) - perfect performance, instant loading times, no stutters, no mouse lags or any lags, but completely suspends code while pressing Alt.
In other words if you play on Windows 10 and if you'll find a way to rebind keys use dlls from 3, otherwise use hires patch dll.
GL&HF!