Hi Alex,
the FXScript DVEs came with Final Cut Pro 3 and Final Cut Express 1. Do you see any FXScript DVEs folders in your effects tab?
Of course, when you don’t see any difference between the original FCP Cross Dissolve and the CGM Cross Dissolve, you can replace them.
The CGM Cross Dissolve is always smooth because the transition isn’t just linear like Final Cut.
All the best,
Klaus
Klaus Eiperle, CGM Plug ins for FCP/FCE: https://www.cgm-online.com