So I just installed the planetary pack, and then the latest version of PRACX and scient's unofficial patch. I also activated widescreen resolution by putting DirectDraw=0 on AlphaCentauri.ini (iirc).

I'm only on the Build scenario since I'm learning how to play, but the game would randomly crash. It would sometimes crash when a new scout patrol is spawned by the 2nd base, and it just crashed after a new mind worm enemy is detected near the 1st base. I was rather happy when the game wouldn't crash after a scout patrol spawned for some reason, but now it's getting really annoying.

Those patches are unofficial for a reason. Uninstall them, and see if your problem goes away.

Crashes also seem to depend on OS and which version of the OS. I'm not having any problem on the latest greatest Windows 10. I did have some problems a few years ago. I think Microsoft has been quietly fixing an emulation layer.