rkr ... no doubt you will get as many opinions on this as you would if you asked "what keyboard is best" ... and the answer is just about the same ... "whatever works best for YOU !!!" ...
Back when we lived in Staten Island, we had a house with a pool when our kids were between the ages of 7/4 through 17/14 ... we left only because of a company move ... In fact that pool is still standing (it was an above ground that we put 1/2 way into the ground) ... during the summer our house was the family meeting place on weekends ... b-b-q every weekend, and of course on Sundays that included pasta and ALL the trimmings ... I hated when I had to leave the 'party' to go play a gig, which was every weekend ... our kid's friends used to come over to our house, so we always knew where our kids were ... I was REALLY into running at the time, and many a time after a run I just ditched the running shoes and dove right in ... was it work? sure, but the stuff they have to automatically clean pools nowadays makes that a lot easier ... do I miss it? definitely ...would I do it all over again? ABSOLUTELY !!! ... only this time I would go completely inground ... is it an asset? ...probably not, but you're putting it in for you, not the next owner of the house ... Now if all of the above turns you OFF, don't get a pool ...
I know this doesn't answer your 'technical' questions, but I wanted to give you the view from the 'positive' side ...
As far as size and shape, it depends on how you are going to use it ... if you really want to swim, it's got to be long enough to do so ... if you are more concerned about the aesthetics, you may want to look at a nice kidney shape ... as I said, a lot of it is up to you ...
t.