Coming from the ST community, and with a 330whp fiesta st (1.6 ecoboost), I trust Adam with this platform. What he's saying is exactly in line with how power bottlenecks have been addressed, and the maverick is no different. The only people that will tell you that you need an intake or exhaust...
Getting the drop in vs spray in has nothing to do with chance. Check your build sheet, if it says you are getting a spray in liner then that's what you're getting.
I've been doing a LOT of looking into wheel and tire setups. If you want a sporty tire, pretty much anything that comes in a large enough diameter will require a 20 inch wheel. With a 19 you'd either need to run a slightly smaller than stock diameter tire, or step down to a high performance all...