Welcome to TFP,
Maybe you can provide a little more info on type of pool equipment, estimated gals of pool.
Definitely would go with 3ft 6in min depth as 3ft just too shallow especially with seats and baja shelf being shallow.
The salt water system (salt water generator or SWG) is the way to go. We decided on that with our pool build because it'll save money in the long run. I don't know if your area bakes in the summer heat but you may look at a chiller if you do. Or a heater for the winter. I mean if you have money you can get all sorts of neat stuff! And if you have dust storms you should consider some sort of cover. Any of these topics can be searched on this site in the bar at the top of this page (blue area). I found a lot of answers that way -- Or on You Tube -- Or looking up pool builders in my area and going to their web page and see what they say. I've found pool building a pool takes a lot of research. Find a good pool builder and lean on him. This forum is extremely helpful. Good luck!