I've seen both of them live (separately of course=Hendrix in 1966 and ELP a few years later. I don't think they would have been that sympatico--in showmanship as you say, yes, but Emerson was much too bombastic to be experimental in the way that Hendrix was. A much more congenial pairing would have been Hendrix and Soft Machine (who also toured together--where I saw them). In fact, Robert Wyatt recorded much of his epic "Moon in June" in Hendrix's home while the latter was on tour. And previously, Soft Machine was grateful enough to thank Hendrix ON THE RECORD (see my article https://medium.com/@slhale/soft-machine-gives-thanks-to-jimi-noel-and-mitch-31ca60ac1133 ).

The organ solos of Soft Machine's Mike Ratledge have been compared to Frank Zappa's guitar work from the same period. Now that would have been a pairing.

For actual prog with a guitar wizard, check out National Health (featuring the sadly unknown Phil Miller) https://youtu.be/vcmFGrUK6ZE?feature=shared