Nah, it's different versions; either you play with or without OPCF. Messed around a bit in the past to make it switchable, but couldn't quite get it right in SH4. Now in SH5 I could do it with the scripting, but then the mod becomes less usable due to incompatibility with other mods.
The brightness isn't about gamma, it's about opacity. To "simulate" light-loss, a partially transparent layer of black is added, making the image darker. The light version just has more transparent masks.
As far as I know the patches are compatible, but let me know if you get overwrite warning with his mod.
