Let me clarify my questions:
Are the R and the RX the same PCB? Is the power socket different?
How many different power sockets are there amongst all Duos? I'm not interested in wattage since they are all the same, just the sockets.
Btw, this "clutch" thing is news to me. I have no doubt that the RX CD-ROM assembly would fit a US Duo, but I don't know if that's the answer to your problem where CD-Rs get the laser stuck. The reason I say this is because I actually have a US Duo CD-ROM drive in my Duo R and no CD-R has ever jamed that system. The US Duo the drive came from would jam however, so I think that "issue" (if NEC even knew it existed) was probably solved in the controls somewhere.