It's only like 15mm further out than stock since the stock wheels are the same width on an Ecoboost PP car.+30 is really aggressive in the rear. I'd like to see someone try it.
I think the +20 might work in the rear but probably not worth losing the ability to rotate tires. I wanted to run a 265/40R19 also over the stock 255's but there are hardly any choices. The only thing i saw i would run is a Pilot Super Sport and they were $315 each with my discount.30 should be fine with a 9" on the rear
10.5 with a 45 is golden
It comes down to a few things really. Aggressive offsets are great however, they limit your ability to run many larger tires due to rubbing. 10.5 with 45mm offset is the absolute lowest offset I would run, 10 inch with 38-40 is the lowest, 9.5 inch with 33mm is the lowest and 9 inch with 26-27 mm is the lowest offset.
Those offsets and sizes are already aggressive, anything else you'll need that "stretched" tire look.
Let us know if we can help you out, we've been personally testing as many wheels on our car as possible.