Its generally a better idea to remove the PA for oral. Most partners just don't appreciate the jostling of the metal against their teeth. I generally wear a CBB, so it is quick and easy to unscrew one of the balls and slip out the ring.
As for sex, I've had a few people that were apprehensive at first; but after playing for a bit, I've never had a bottom complain. In fact, most talk about feeling the ring by saying that they felt 'full'. Bottoms describe feeling the ring during sex and they considered the sensation to be quite pleasurable.
For me, I decided upon a PA because I simply like the look. My PA is simply an adornment. The first six months or so after being pierced, the sex was incredible. Best orgasms ever. The feeling eventually tapered down. Don't get me wrong, its still great to orgasm, but it is not the earth shattering orgasms that I had experienced following the initial piercing.
Best of luck to you. Based upon the feedback that I receive, you won't be disappointed.