Ah yeah. dgVoodoo2 causes some other issues with framerate (dynamic lighting in particular.) You might have luck trying to use an earlier version of it. I haven't used DXVK with this, so that might also be causing a bit of a drop.
Regarding the scope issues..
The game originally performed (to my best guess) a screen lock to manually adjust each pixel colour whenever the game would call "FillRect". I created a class to scale all FillRect's to 32x32 and cache them, then use a ScaleBlit function to more quickly perform the same operation without the need of a screen lock.
I know there were a few folks using Wine to run the game, and they didn't have much trouble with it, have you tried not using dgVoodoo2 and DXVK?
We unfortunately don't have the renderer's source code, so we can't improve on this behaviour. Hopefully one day, someone can figure out the rights issue with the NOLF franchise and do a proper pass on these games. NOLF 1 especially needs it