@mitu Omg it worked!!! Much appreciated man.

@sirhenrythe5th Got it! So it does supported it just not my file names. I changed them from CD1 back to CHD works like a charm.

Use the default retroarch.cfg - leave aside all the hard sync settings (I don't think they're relevant for the Pi's GPU) and the audio settings. Also, a GPU mem of 256 is more than enough for most emulators, so I don't see any point in upping it to 512.

Thanks for the reply.
Removing the line autospawn=no enabled PulseAudio again if I'm not mistaking.

Already tried the 3rd answer on that thread with no luck.

Just to give this thread and all you guys some closure, I have not experienced any slowdown on PS1 games since installing Retropie 4.4 from scratch. Perhaps it's the new version, perhaps it was some tinkering I had done and that has now been erased. I did notice that PS1 games tend to slow down on my Pi2 when enabling enhanced resolution, either with or without the speed hack. I have not yet tampered with the overclock settings and I'm not sure if I should, since it's a Pi2... Otherwise I'll simply stick with the bilinear filtering option, which slightly improves graphics, and wait for the Pi4.