Here you go. The stock wrist pins are pressed into the rod, but the pistons float freely on the pin. If it wasn't floating on either the piston or the rod, the piston would not be able to go up and down the cylinder without getting seriously messed up. Fully floating wrist pins are not pressed in, and therefore are called fully floating pins.
Now for the oil passage question. How the hell else do you think oil gets pumped up into the oil ring? If you didn't have a way of getting oil into the oil ring, the rings would get so hot they would melt to the side of the cylinder wall. Not to mention the wristpin/piston bearing surfaces need to be lubricated, or else you would have some major rubbing going on. Hope this helps. When in doubt tear the block apart and study it for a while. It's actually real genius how they get oil up in places. At least I was amazed. I don't see how fully floating wrist pins will add hp, unless they weigh a hell of a lot less, and are just decreasing the reciprocating mass.