Well probably nobody has done all three, and if they have then probably not in the exact car. A lot of people have compared the SH and the VX, since I understand both can be had through the engine exchange program, and a few people have upgraded from one of those engines to the OS.18 CVR (or is it CVRX?).

I've only ever run the VX engine, but my understanding is same as you - that the SH is a step up and that the OS would be a step up again. How big is a step? I dunno, but the VX responds well to a better tuned pipe, so that's a cheap improvement. Perhaps put a better pipe on, run it slightly lean for some more power, and if you blow it up get the SH for half price using the Redcat engine exchange program.

IMHO outright top end is not a good metric for checking engine performance though. I tune my engines to rocket through the midrange since that's where I drive. A sweet running max-rpm might give pretty poor punch off the line, and vice-versa (especially if you'd rather just drive than take the time tuning)