To force 1920x1080, you have to edit the dgVoodoo.conf file it creates, or use a tool like IGI Resolution Patcher alongside dgVoodoo. The 2021 wrapper handles the rendering; a patcher handles the UI stretching.
To play the original Project I.G.I. (I'm Going In) smoothly on modern hardware, using dgVoodoo 2 dgvoodoo 2 2021 download for igi 1
If you want the absolute best visuals, combine DGVoodoo2 2021 with DgVoodoo2’s Anti-aliasing. In the config tool, force 8x MSAA. The game’s wire fences will stop shimmering. To force 1920x1080, you have to edit the dgVoodoo