Hi there Fahed
In my experience so far in Israel Ipe doesn’t need any extra treatments other than a good sand and oil some weeks after installation for best results. Nor have we fitted pre-treated boards as far as I’m aware theres no need for special pre-treatment. For the substructure I recommend wood in 90% of cases, exceptions being where your base will stand in water(like around swimming pools) or places where you havent the height to use normal material.
We fit both KD and AD ipe from deck to deck depending on the source/budget, both are fine to work with in our climate but I would recommend as you want to use a hidden fixing system to source and fit narrower boards, 14cm ipe can release itself from the clips over time through shrinkage and movement, keep in mind the less material in the board the less it can shrink.
Best of luck