Locate your ini file in your steam folder:

\Steam\steamapps\common\DoDonPachi Resurrection\Daifukkatsu.ini

Open it in your editor of choice, I recommend Notepad++

The ini settings that worked for me:

If you can rotate your 2K monitor, set zoom to 150%. Hear me out:

PCB runs 1x 320x240
360 runs 2x 640x480
100% runs 4x 1280x960
150% runs 6x 1920x1440

It uses the full width (height) of your monitor, and looks good without smoothing.