Lariat, XLT, XL, et al are all trim levels. I think the STX is a basic truck that is a V6, but I'm not certain. The Harley Davidson and the SVT Lightening are upper end motors (perhaps the same motor) with different trims. XLT will have electric windows and door locks, the XL is reach-across. The Lariat is also electric with extra cup holders.
I have a '97 XLT that I like alot. I wish I had the super cab -- the one with more space behind the seat, but not the 4-door. I think the 4-door is the Super Crew or Club Cab, or some name like that. Whatever. I have no use for a 4-door pick-up truck. I could use more space behind the seat I sit in though -- the dog needs her space, but I wasn't thinking ... The dog doesn't need doors, just space.
In any case, I have electric locks and windows, Cruise Control, AC,
6-speaker radio, sliding window on the cab, tachometer.If you like door locks and electric windows, and don't need the huge motor that the Lightening or Harley's get, then you will be happy with a Lariat or an XLT. I have the 4.6L Triton motor. You want the 5.4L. Mileage will be comparable, but the power of the 5.4 is useful.