Welcome to the FRF. Good looking truck! I highly recommend getting rid of the tint on windshield unless you only drive in daylight. As for the rust, I’m from FL as well and some of my family & friends have rust like that. Driving on the beach, or on roads that sand either blows up on or gets dropped there from vehicles that were on the beach, can actually get as salty or worse than northern states. My 2020 looks nowhere like near like yours, but every time I come back from beachside, I run my Raptor through a car wash with UNDERBODY WASH to get the salt off. I would not undercoat it since you will only encapsulate the rust. I’d get as much off as I can , and then spray with some anti rust treatment. I’ve never been a fan of undercoat after living in Wisconsin and New England for 55 years until moving south permanently. Undercoat is very dependent on how and when it’s applied, and what’s under it.