Yes

Yes. There are so many variables but throttle input seems to have the biggest effect on the gauge reading. I can have a wide difference in MPGs at the same speed on a relatively flat highway. I do most of my driving in the city and can get better mileage than I get at times on the highway, if it is not stop and go. If I drive 40-60 MPH on a flat road with no stops I can get MPG readings of near 30 MPG. At 70-75 MPH I generally get low 20s, but at those speeds the road can have more changes which affect the readings. Overall city MPGs average in the upper teens. Cold weather and stop and go traffic can have a large effect on the city readings. I do have 3.73 gears which could affect the highway mileage some and perhaps benefit city driving. Some others have mentioned sustained MPGs in the mid 20s with the 2.7L.

I have an XLT which does not have a boost gauge standard. Higher trim levels have the boost gauge and I'm sure some have added it to their XL/XLT trucks.

Many of the F150 forum members claim lower MPGs with the 5.0, which seems to be the consensus. The 3.5 Ecoboost is between the 5.0 and 2.7 in terms of mileage. The 5.0 with the 10 speed seems to be a better match than it is with the 6 speed.