Yeah, there are 2 POPStations now. The original, which creates single-disc eboots, and POPStationMD which created multi-disc eboots. Popstation is pretty janky anyway. I recommend switching up to RS GUI POPStationMD v3. It's a GUI-based PSOne ISO->eboot converter that can handle both single-disc and multi-disc eboot creation. Fantastic.
Definitely upgrade to 3.90 M33-2 (you can use the newly coopted Network Update to do that from now on. No more manual updates!)
The 1.50 patch restores 1.50 kernel functionality to PSP fats only running post 3.52 M33 firmwares. From 3.71 M33 on 1.50 kernel mode was stripped out by default. Unless you're using some kind of emulator or homebrew app that absolutely requires 1.50 kernel access, I'd avoid installing the patch. Also, chances are, if you DO have an app that requires 1.50 kernel access, then you're using an obsolete version of it. Most of the more important apps and emus have been ported to the 3.7x kernel already.
Finally, you'd best look into downloading and setting up Dark Alex's 3.80/3.90 POPSLoader plugin. It allows you to store just about any version of POPS (the Sony-built PSOne emulator). Not all POPS are created equal, and certain games often run best on a specific version of POPS. Without this plugin, you'd only have access to POPS 3.90, so it's quite possible that PSOne games that were working on your 3.52 M33 machine will no longer work. POPSLoader is what allows you to load POPS 3.52 (or just about any other POPS version) on your 3.90 M33 machine. Crucial for those that play loads of PSOne games, IMHO.
Definitely upgrade to 3.90 M33-2 (you can use the newly coopted Network Update to do that from now on. No more manual updates!)
The 1.50 patch restores 1.50 kernel functionality to PSP fats only running post 3.52 M33 firmwares. From 3.71 M33 on 1.50 kernel mode was stripped out by default. Unless you're using some kind of emulator or homebrew app that absolutely requires 1.50 kernel access, I'd avoid installing the patch. Also, chances are, if you DO have an app that requires 1.50 kernel access, then you're using an obsolete version of it. Most of the more important apps and emus have been ported to the 3.7x kernel already.
Finally, you'd best look into downloading and setting up Dark Alex's 3.80/3.90 POPSLoader plugin. It allows you to store just about any version of POPS (the Sony-built PSOne emulator). Not all POPS are created equal, and certain games often run best on a specific version of POPS. Without this plugin, you'd only have access to POPS 3.90, so it's quite possible that PSOne games that were working on your 3.52 M33 machine will no longer work. POPSLoader is what allows you to load POPS 3.52 (or just about any other POPS version) on your 3.90 M33 machine. Crucial for those that play loads of PSOne games, IMHO.