Virtually every boat builder that still uses wood, uses PT plywood, it's KD so it works well, you can get this wood, but it's not easy to find for a DIY'r sometimes.
As mentioned, if glue or adhesive is used between the stringer and hull it's for three things, it spaces the stringer off the hull so you don't create a hard spot, it holds the stringer in place so you can easily work on it, plus it creates a radius so you can easily laminate it. Small boat builders didn't typically use anything, they pre-made a wooden stringer grid and dropped it in place right on the hull, then glass it. So in a way, it makes no difference how you do it.
The "which resin to use" question comes up often, the true answer is, it really won't make a difference, polyester or epoxy will both do the job and it will out live you, so pick one or the other and get it done.
People will choose a product or method to use, sometimes for good reasons, sometimes for no reason other than it makes them feel good, and it doesn't make much of difference because it's their project and doing it how they see fit is part of it.
