First thing you need to do is figure out what you can tow. Your payload may limit you to a pop up.
On your drivers door post, should be a tire and loading sticker. It will have a number for weight carrying capacity (payload) as the truck was configured at the factory. F150's can have a very wide range in payload. Some as low as 750 lbs, some as high as 3200 lbs. They're not one size fits all.
Everything and everybody you put in, or on the truck, takes away carrying capacity, pound for pound. That includes aftermarket accessories (bed liners, bed caps, step bars, suspension mods, even floor mats), people, cargo in cab or bed, weight distributing hitch, and tongue weight from a trailer.
If you're unsure of aftermarket add-ons, fill up gas, weigh the truck, and subtract that from it's GVWR. The remainder is your available payload.
From your payload, subtract the weight of your family and things you would normally take along (car seats, coolers, luggage, tools, bikes, etc) in the truck. If you need a weight distributing hitch, subtract 100 lbs for it. What ever is left, is available for trailer tongue weight. Divide that number by .13. That will give you a ballpark figure of what loaded trailer weight, would put you at max weight.
Here's a calculatorYou may find, a pop up provides you the most space at the least weight. Pop up will also give you better MPG. Next up might be a Hi-Lo. As mentioned above, good MPG and travel trailer, don't go together.
With a high walled trailer, it's the front wind resistance and rear drag, that affect MPG the most. Within a couple weeks of each other, I towed a 25 foot / 6000 lb trailer, and an 18 foot / 4000 lb trailer, on the same road, same truck, and had little to no change in MPG.