This is an interesting topic to me. For me, my experiences fall into 3 categories:
1. For some reason, since my RP, I am very, very sensitive (in a good way) to touch and stimulation. I can combine that with slightly contracting/twitching my pelvic floor muscles (i.e. Kegels) and get waves of sensations that are pretty darn good approximations of orgasms. My pelvic muscles seem especially well developed, strong, and controllable -- probably from all the Kegels. The good thing about this approach is I can do it multiple times and can make it last a long time. These never fail for me and are always a good option. And, I can proceed with 2 and 3 below after I have enjoyed this for a while.
2. As others mention, and most of the time for me, my "traditional" orgasm peaks and goes away very fast .. not very satisfying but better than nothing.
3. Only occasionally/rarely: I have an orgasm that is beyond amazing .. so intense I can barely get through it .. far beyond the old days. I want more of these .. not sure what to do to accomplish that. It may be mental since these tend to happen when I am not concentrating or worrying about it .. they just surprise me. Wonderful when it does happen .. just not very often.
All of this is independent of erection (pump or trimix) or no erection.
Finally, I am on HT, so I presume the lack of testosterone messes with my orgasms. But, only time will tell, when I finally get off HT.