From what I've tested, it seems like the Pro Action Replay function to disable the region lockout is always active. My USA Saturn was loading Japanese ISOs just fine.
I have one of the newest blue Saroo SSHD Loader carts, tried Dodonpachi and Dynamite Deka, works great. Yes the loading is lightning fast.
I'm gonna load up my ISOs on it including prototypes and translations, we'll see how those fare.