Hello,
I will be building a 16x16 pool deck real soon too.
Here are some things you have to consider when building a deck beside an AG pool.
First off - do you have frost??
If you don't EVER have frost, you can go over the top rail and put a fascia board along the front edge of the deck - this gives a really nice look, hides the rail behind it and you can climb right up on the deck without any worry of denting a top rail.
However, if you experience frost, then neither of your thoughts are a good idea, mainly for the following reasons:
(here I'm talking about a deck built on deck block)
Frost is unpredictable and the expansion encountered is relative to the moisture content in the soil - meaning you can have a spot that heaves 5" right beside a sopt that heaves 1" because there is a depression collecting water beside a hump that drains it.
So, your pool structure could heave more than the deck, so if the deck overhangs the pool, the structure will crush into the underside of the deck.
If your deck heaves more than the pool structure and you went under the lip, then the deck could tear your pool structure upwards.
The best way to do it in a frost area is to go beside the top rail leaving a 1/2 to 3/4" gap between the two structures.
There are also other factors, if you use footings that go below the frost line, the deck will not move, but the pool still will, you could go below the rail (never above) this way, but if frost heaving cause the ground to shift/settle, your pool may come down lower than it was last year and start to sit on your deck.
Go here for some nice pool plans, I'm going with the 16x16 side pool deck using composite as my floor likely picture framed around the perimeter since you can arc composite esily enough and finish it off with Aluminum Railing.
http://www.deckplans.com/Plans/PlanType.asp