I think you know the answers to all these questions. 4-cylinder engines only require 1 head as there is only 1 bank of cylinders. Also, large displacement 4-cylinders tend to run not so smoothly so clearly OHC is the way to go.
Secondly I really like your choice of word's "Ford's Technology" Direct Injection, Turbocharging, and smaller displacement is something Ford did not invent, plenty of other manufacturers had done the same thing before including GM. Ford just happened to attach a name to the technology and market the crap out of it.
Comparing the current 3.5 Ecoboost and the 6.2 V8, the 2016 Lincoln Navigator has the highest hp/tq ratings of all the Ford products using the 3.5L displacement Cyclone block. The Navigator makes 380 hp @5,250 rpms and 460 lb/ft torque at a very low 2,750 rpm. In 2WD configuration it get 16/22/18 mpg and can tow 9,000 lbs.
Now the GM competitor to the Navigator would be the Escalade. The Escalade has a 6.2L V8 that makes 420 hp at 5,600 rpms and 460 lb/ft at 4,100 lbs. In 2WD configuration the Escalade gets 15/22/17 mpg and can tow 8,300 lbs.
Now I would argue why do I need a V6 and twin turbochargers, which Ford claims improves fuel economy by 20% and reduced emissions by 15%, when in an objective comparison it's just about equal in most respects to a naturally aspirated V8. Ford has the edge for 2WD, but when you compare 4WD the GM K2xx trucks with 6.2L V8 beat the Ford EcoBoost products in highway mileage.