Nice deck hrsdennis, I put one up 2 years ago and it looks very similar.
As for over, under, or flush with rails, I built mine over the rails but left about 2 inches clearance between. I have a stainless ladder that bolts to the deck. It has worked great for me in PA.
However it is a real pain trying to cover the pool at the end of the season.
Imho it's a matter of preferance but do consider what you will have to go through later to cover and uncover the pool.
Hope this helps.