I have a Walther PPQ. From what I have read some people really think the couple hundred bucks are well worth it to get the PPQ over the PPX. But I haven't shot the PPX, never even heard of it till this thread. That said at the same time a lot of people really like the PPX.
But buy the gun because it fits great in your hand and you enjoy shooting it, and then on looks. For me personally the walthers just fit my hand perfect. I don't really mind the barrel sticking out, I just dream of a day where I can spin a silencer onto it.
I couldn't find a compensator for the PPQ or the PPX with google, lots of people talking about it though.
I really enjoy Walther guns, and kick myself for selling my P99 all the time, need to pick one up one of these days.
I'm not sure the over all length of the barrel, but you could probably get a non threaded barrel for it.