You're asking why a 5.0 litre engine with double overhead cams doesn't have the same push off the bottom an engine with 1.2 litres more engine displacement does?
Umm, that push off the bottom is about all the Camaro engine has; it gets pretty asthmatic at 6000, whereas the Coyote is singing there.
The stock tune is pretty soft on the Mustang, though, so much that it is really a must do, in my opinion, just for general all round enjoyment. At this point, I'd pick a respected name like Steeda and go that route. No engine failures, ever, on that tune. You could pick Ford's Procal but, you are almost through the warranty period that tune covers. It really perks up the bottom end hard though and I've shoved my loaded car in the 11s on that tune.
A little light whine from a steep geared (3.55 or 3.73) 8.8 is pretty normal stuff. If it's loud, obviously not but, you might see if someone has some aftermarket suspension bits back there that are amplifying noise.
2014 Premium GT, SGM, Brembo, Auto, Tech, Comfort, etc. GT500s, Steeda UCA, VMP auto N/A tune. 100 shot nitrous on BBR tune. Best e/t 11.42 at 120.64
2012 Premium GT, Candy Red, Brembo package, 3.73, MT82, Comfort, Tech, et al. Procal tune, Roush UCA, UMI poly LCA, GT500s, Steeda red bracket, Hoosier 28x10x16 bias drags. Best e/t 11.91 at 115.23 RIP