PSO Episode 1&2 has three different versions...
- Ver. 1.0
- Ver. 1.1
- Ver. 1.2 (which is the Plus version)
PSO compatibility on DIOS MIOS is very inconsistent. It becomes even more of a headache when you consider that PSO will only run on certain versions of DIOS MIOS. When you DO find a version of DIOS MIOS that works with PSO, it's only specific versions of PSO that even work. More often than not, PSO doesn't work at all. And, if I remember correctly, the Plus version of PSO never worked on DIOS MIOS. Also, if you wanna play PSO online, via private servers, then DIOS MIOS is not your answer.
Another option is to try Devolution. Devolution requires the actual disc for verification (which is inconvenient) but it gives you the ability to play the game online via private servers.
My personal preference is Nintendont. You don't need to mess with disc verification, and it has a high compatiblity with the GameCube library. The one negative is that it doesn't allow you to play online via private servers. Although, if you don't care to play online, then Nintendont is you're best option AND, I know for a fact that the Plus version of PSO works with Nintendont.