If you look in the video setting for OpenXCom, on the right is a setting for filters. These apply post processing effects to the screen, and they are pretty resource intensive compared to running with no filter.
"Disabled", "Scale", "HQX", "CRT-interlaced*", .... I'm not even sure if I have GL-accelerated hardware - it's not a factor I consider at all when buying machines. I'll try several, but the list is long.
"Scale" and "HQX", "Curvature", "HQ2x", "OpenXcom*", "Pixellate*", "Quillez*", "Row*", "SABR-XCOMified*", "SABR*", " scale4xHQ*", " have no visible effect on my system.
"CRT interlaced*", CRT-simple*" and "CRT*" introduces a curve, and lines reminiscent of an early 1980s glass teletype. Even I had a flatter, squarer tube when I first brought a PC (which was pushing 7 years old when the original game was released. Clearly a modification for the sadomasochist fraternity.
"Phosphor-simple*" has a slight effect on colour balance, as if your blue gun were under-current.
"dot_n_bloom*" just makes things dim.
"heavybloom*"makes it look as if your guns are flat-out misaligned.
"simplebloom*" is between the last two.
From the "*" modes working, I infer that I do have the appropriate hardware acceleration. SHRUG, but I'll file that information somewhere on the grounds that it might be useful somehow.
Ah, there's a setting for "grab mouse", which I had been wondering about.
OK, what were the poll questions? I don't see any reason I'd use any of these tweaks.