I've got an Apex, and it really does add some distance. I'd say maybe 50 feetish, which can be a big advantage in a 1 hit game. There are some drawbacks to it though. I was put off by the aiming adjustments so I eventually stopped using it, but some other guys I play with swear by it.
-The balls go further, but the further they go the less likely they are to break. Once you get past the range of a barrel without it, you'll get a lot of bounces, so you end up shooting more.
-The tip itself has some diameter to it so if you're used to closely looking down the barrel, you might find that you're not aiming as well.
-The ball rolls/bounces off the upper part of the apex tip, so the direction the ball travels is at a slight downward angle. To correct and get the range you have to slightly point your barrel upward. This takes some getting used to.
Its also worth mentioning that it you end up with the apex, it adds something like 2 1/2 inches to the barrel's length. If you use the J&J, the removable adapter is another inch, so your 14" barrel would be somewhere in the 17" range. So, I'd suggest the shorter barrel. If you decide against the apex, well the 16" might have more porting depending on manf., and for someone trying to do long shots I'd think that the extra length would let you sight down it better.
Nice gun btw
Oops, lemme give my opinion on the paint question: For doing long shots, don't buy the cheapest stuff, and buy fresh paint from a local pro shop. The $60 stuff flys straighter than the $40 stuff. Marbs or Premium, are both really nice examples.