I bought a 2017 F250 6.2 a few months ago and I am impressed so far but haven't put it to long towing test yet. It replaced my aging 2001 Silverado 2500HD with the 6.0. I wish I could have found a 4.30 geared F250 but they are hard to find in the used market.
I asked a few shops about the 6.2 and only one mentioned an issue with the valve timing but they appear to be very reliable.
Ford allegedly reworked the heads in 2017 and squeezed out an extra 30 lbs of torque and the torque curve peaks at a lower RPM. This data looks interesting on paper but I don't know if you could even tell the difference between the pre and post 2017 6.2s.
I haven' tried the E85 so I cannot comment on MPG ratings there. Running around town, I get about 11-12 MPG on regular (87 octane) fuel.