The impact on MPG would be extremely marginal, if any at all
i May be missing it but do you have the link to this specific one ?AVS II uses the existing rivets but may stick up more than you like.
This is the one for a 2019
I just noticed your post. Do the rust spots look like flecks of rust? If so depending on where you live it could be acid rain. I first saw those in 1989 on a white Acura legend. We tried to buff them and ended up repainting the hood as we scratched the daylights out of it. I hope you didn't see this too late.
It's possible that's its rail dust too. I've seen where tiny particles can get imbedded into the paint and if you don't clay your vehicle it will eventually rust. You'd be surprised what contaminates are in the paint even when brand new. While you're washing it take a plastic bag and stick your hand in it and rub the panels on your truck. If it feels gritty then it needed to be clayed. Once it's clayed it'll feel smooth as glass.
I just bought that same one also. It looked to have the best possible upward bend to help deflect rocks etc. Most other look like they lay flat on the hood. It was pretty easy to install but be careful as the hood seal tears easily. I know I pulled on of the original clips wrong and ripped the seal. Plus I like the look on my rapid red Ranger.
