You need to use a 64-bit bottle to make this run at all (I used Windows 10 64-bit). When I ran it with a normal (32-bit) "Windows 10" bottle, it would not launch at all, giving errors in the log saying:
"0009:err:process:create_process 64-bit application L"[...Path...]Games\\The Witcher 3 Wild Hunt GOTY\\bin\\x64\\witcher3.exe" not supported in 32-bit prefix"
You then also need to install DXVK into the bottle (easy as it has a Cross-Tie). Without it on 18.1 I could not do much beyond launching and playing the intro movies. I could start a new game, but could not actually play, with terrible graphical issues, frame-by-frame speed and then a hang.
With CrossOver 18.1 and DXVK (using the nVidia proprietary drivers on Ubuntu 18.10) it is playable. I only played <30mins, but I ran around, had some conversations, killed some monsters etc. There were some graphical glitches and it wasn't as smooth as running the game on Windows on the same machine, but it was playable.
