I can tell you from experience, you will know if you are under powered.
I spent 10 day in the Ozarks towing a 5000 lb. dry weight TT with a 200 hp V6. The odd thing was, in spite of the diminutive motor the F-150 had a towing package and suspension upgrade so weight was not a problem.
The problems with under power are,
โข Lack of acceleration when pulling out or trying to pass.
โข A max speed of 62 to 65 mph on the flat.
โข A struggle to maintain 50 to 55 mph on anything that resembled a hill.
โข Most importantly, it took a keen amount of accelerator playing to keep the engine from dropping down into a lower gear and creating excessive motor rpms.
We were kind of lulled into a false sense of security by the towing package but decided to rent a TT to see what this RVing was all about.
Other than the annoyance of an underpowered TV we also discovered,
โข A 250 to 300 mile day was quite enough.
โข You have to like driving at 60 to 65 mph and being passed by everything on the road.
โข There are no fast moves or last minute decisions when pulling one of these barns down the road.
โข RVing suited our touring life style. We like it but it is not for everyone.
โข And finally you will get about 10 mpg.
Still it is up to you to decide what kind of TV/TT combo suits you.
Twenty six foot 2010 Dutchmen Lite pulled with a 2011 EcoBoost F-150 4x4.
Just right for Grandpa, Grandma and the dog.