Go 5Star if you own a Gen2 and want a tune. You might be well on your way to a new truck by the time FP releases their tune. Enjoy your truck now.
Regarding warranty, it's been my experience Ford Warranty is mostly arbitrary anyway. I've seen dealers decline work that should clearly be covered and I've seen dealers get approval to warrant work that is well outside the written limitations.
It's all about what dealer you go to, who you may know or what service advisor you may draw, and most importantly, your attitude.
It all depends on what you’re going to do with the truck. If you’re going to daily drive and hold on to the truck for a while, an aggressive tune might not be best for you. OTOH, if you have enough to cover a motor or hard part replacement and are willing to forego the warranty, then an aggressive tune would be more entertaining for sure.
Aftermarket warranties are underwritten as an insurance policy, and I can tell you first hand that if they see anything - and I mean anything on the vehicle that is not a factory part, their adjuster reports to the underwriters and they deny the claim, policy verbiage be damned. Allstate denied my coverage (at first, second, third, 4th and 5th ) for “installation of aftermarket parts”. I pointed out their policy did not create an exclusion for this, only aftermarket parts directly related to a failure. My agent and the mechanic penned a letter indicating the parts in question would not and could not cause the failure a cam chain tensioner. I forget what the adjuster flagged, but it wasn’t even a powertrain part ! Once the agent and mech wrote the letter, after about a week they knuckled under. My agent followed up and indicated he was no longer writing or supporting the warranty policy after our shared misery.
Just be cognizant that the approach aftermarket warranty companies take is a bit more aggressive at denial than the manufacturer policies.
@Dacuri is right though, if you’re modding quite a lot depends on your S/A, mechanic, service mgr. and you. If you have the gift of being capable of selling a drowning man a cup of water, you’re probably fine.
