First part, I'm not sure about the op-ups. By and large most op-ups have status, but still interested to see what happens (say a GO gets a J-F op-up...does he get F tags? I don't know).

As for the advantage of the priority and first/business class wordings, at HKIA CX does a pretty good job of having the F class tags shoot out first, followed by J class tags, and lastly by non-tagged bags. Certain outports are better than others but HKIA is usually quite good at getting CX's priority tags straight. I presume it must have something to do with where those bags are loaded on the plane (maybe they're loaded in last, and together?), and then the HKIA ground agents are very good at offloading the F tags first, then J tags, then non tags. This is pure speculation, though.

I can tell you, as a DM so I have F class tags (and use HK ID, so I go through immigration in a matter of seconds), I rarely wait more than a few minutes for my bags when flying CX. My bags are frequently among the first five to hit the carousel. It really increases the appeal of checking bags, since I know whenever I'm returning to HK checking my bag is virtually the same amount of time as carrying on. I'm a huge fan. I contrast that to a recent flight on QR back to Hong Kong, I waited for my bags for nearly an hour....despite having J tags!