I have never felt the need to have to clean a barrel. I mainly shoot springers and haven't ever detected a drop-off in performance that dictated a barrel clean. However, I have heard a good few PCP shooters say otherwise and they will advise a clean and re-lead once accuracy drops off. For some, this seems to be a regular "routine" ritual after so many shots after gleaning the information. For others, only when that drop-off is detected.
I have never washed, dried and lubed pellets but understand that this might help in this regard.
At a guess, and pretty much a generalisation, I'd say that pellets from JSB and H&N will be the "cleanest" ex-factory. But the pellet to choose (for me, anyway) would always be the one that delivers the best accuracy in a particular rifle / barrel.