If you're experiencing low FPS, this fixed it for me.

[url=https://pcgamingwiki.com/wiki/Blood_II:_The_Chosen#Run_Blood_II_on_modern_systems]https://pcgamingwiki.com/wiki/Blood_II:_The_Chosen#Run_Blood_II_on_modern_systems[/url]
Download and use the ddraw.ini from here. It's at the very bottom of the section "Run Blood II on modern systems".

I use this in combination with the dgVoodoo wrapper.
http://dege.freeweb.hu/dgVoodoo2/dgVoodoo2.html
The high resolution crash fix + widescreen FOV fix.
[url=https://pcgamingwiki.com/wiki/Blood_II:_The_Chosen#Widescreen_resolution]https://pcgamingwiki.com/wiki/Blood_II:_The_Chosen#Widescreen_resolution[/url]
Install the ddraw.ini after dgVoodoo2, overwriting existing files if necessary.

This is also a good guide that helped me fix the game: https://steamcommunity.com/sharedfiles/filedetails/?id=498599858.

Something like this has to be pinned in the forum, as the game runs surprisingly bad on a modern setup for a GOG release.