this lends itself to that joke, but i'll refrain...
First of all it depends on your routing. many divers choose to route 'Up and over' which allows for a smooth bend in the tube (no kinking) with minimal strain on the catheter and ...attachment point. This also allows for full mobility, a strain relief for full flexibility if you will, in your suit (compared to 'straight down' routing) I am, in theory, a bit shorter than your average pee valve user, but have found no problem with the length that comes standard. I have had some petite divers choose to shorten their tube, mostly because the loop was very large on their small frames.
With regards to residual in the tube, there are a few ways you can handle this. if you close the valve before you unhook, the 'vacuum' will control it while you get your rinse solution, but then you'll have to unscrew it a bit to rinse, and might get some residual on fingers and suit leg. (thats what rinse water is for, right?)
the other way is just leaving it open at all times and then be prepared for the residual drainage (From the tube) when you unhook...
again, no matter which way you choose to do this, flush your pee tube well with fresh water and a disinfecting solution after EVERY dive (a BIG syringe is really nice for this, available at pharmacies and medical supply stores)
after rinsing with fresh water, then disinfecting, its a good idea to 'blow' through the tube which helps get rid of remaining moisture (hey, it's clean now, you rinsed it!)
now it's all clean, and for the most part dry, so the tube flopping around whilst getting out of your suit is not an issue
when diving with your pee valve, position really doesn't matter all that much. you are dealing with fluid in a fluid environment. in fact, what you'll find is that you can utilize it almost any position, in and out of the water. standing, sitting on the swim step of the boat, floating, swimming, etc... Please use common sense though, dive buddies don't appreciate making a puddle in the parking lot during the pre-dive brief