The RMM will fit any Celica just fine, no matter the year. Not sure how well any of them do on a GT, since there haven't really been any dynos of them, but none of those exhausts you mentioned have a big tip. I think the TRD has the biggest at 4" (TPR will be 3.5"), but that's still far from a melon launcher.

Also, none of those exhausts are loud. On a GT-S, they are all actually about the same when it comes to loudness. On the GT-S, though, the TPR makes the best power out of the three by far, but not much is known about any of them on a GT. The only known advantage is that TPR is almost $100 less than RMM ($50 less than TRD), and weighs close to 20% less than either.