When buying a TV/TT setup, you need to keep all the weights / capacities in mind. If you buy the truck first, you need to understand it's capacities, when shopping for the trailer. If you buy the trailer first, you need to understand it's needs (for towing) when shopping for a truck. Towing at, or near max capacity, is not where you want to be.
Personal experience - weekend trips, I (the driver) would arrive with leg cramps, back ache, neck pains, and sometimes, white knuckles. Windy days were the worst. The pain would subside in 24 - 48 hours, just in time to drive home. The longer the trip, longer the time to recouperate.
Things to watch for:
Buying travel trailer:
Advertised weights won't match actual sticker weight.
Weights, listed on the sticker, are what the trailer weighed when it left the factory. Actual weight will go up, before the trailer leaves a dealer lot. Average load for dishes, pots and pans, groceries, water, and camping gear is 800 - 1000 lbs. Ten to fifteen percent of this, will be added to the tongue weight. Average tongue weight is 12 -13% of loaded trailer weight. A 4000 lb trailer will be around 5000 lbs loaded.
Does the trailer meet all of your needs / wants?
Buying a tow vehicle:
Does it have sufficient room and payload to support all of your planned cargo, passengers, and tongue weight from the trailer?
Forget about advertised numbers for max tow capacity. You will run out of payload, long before you get to that number. Consider everything and everybody you plan to put in, or on, the tow vehicle. Every pound you add, subtracts a pound from that vehicles ratings / capacities. Give yourself some room for unplanned passengers or cargo.
Many manufacturers build a line of vehicles with the same model number and many variations in capacities. F150, for example, can be found with 750 lb payload and 5000 lb tow capacity, there are versions with 3100 lb payload and 11,000 lb tow capacity, and many in between. Not just any F150, could handle the trailers, you are considering. Ford is not alone in doing this.
Lite trucks and SUV's are built for passenger comfort. Specifically, their tires and suspensions are not built for carrying heavy loads.
As many of us can attest to, the first trailer normally leads to a second (bigger) trailer. Is the tow vehicle up to that task?