When you find that "perfect trailer" you will know it. Stay below the listed maximum for your tow vehicle and all will be well. Looking back on my trips around this country I cannot remember or even care what gas mileage or even the cost per gallon....all I remember is the trip and enjoy viewing all my photos decades later....stay focused on the important things. Don't buy a cramped Travel Trailer that you will regret ever owning. Dealer's lots are loaded with trailers that were traded in because they were too small to enjoy.....don't add to that inventory!
Happy Camping!