Strange graphic glitch in gzdoom

I recommend to use GZDoom 3.5.1 and not the newer,
the newer ones have graphics glitches.

I recommend to use true color software renderer over OpenGL
it looks better with more colors and less dithering and does not blur the game sprites.
Thanks, can I enable software rendering in the INI file? Can you tell me what flags to change or point me to a guide that details what everything does? Any help would be appreciated.