[Jäse]

HP is derived from torque and RPM. Higher HP = torque at higher engine speeds. That's why diesels don't make much HP. They don't spin fast. As for the feel during daily driving...all you're ever going to feel is acceleration. If you take an Expedition with 500 HP, then increase the weight by 50%, the feeling is going to change, without any change in the powerband.

The 5.0 has more HP potential because it is larger and revs higher than the Ecoboost. As a naturally aspirated engine, it has to rev to make more power. In contrast, the Ecoboost can use a larger or faster spinning turbo to make power. That doesn't change by adding a supercharger. The 5.0 will still rev higher, but now it has the additional benefit of boost. More airflow + more RPM = more HP.

 

[Jäse]

also, being that the 2017 3.5 was a new gen engine with port injection, can I use 2017 (gen 3?) heads on my 2017 and tune for that on a 2016 ecu to get the benefits of increased fuel delivery and valve cleaning?

I think this is one of things where you'll hit diminishing returns. Even if it's technologically feasible, how much effort would it take to get an ECU and install wiring to control the port injection system? You'll probably hit power limits on the block before you run out of fuel. I'm on 144K on my 3.5 engine...as far as I know, no issues with gunky valves. Just manifold leaks and possibly timing chain. One option might upgrading the HPFP and in-tank pump for E85, if you have that near you. It's some additional measure of protection over detonation as compared to pump gas.