Lots of good advice on this subject in previous posts. I have a different situation which you should consider during your purchases. This might not apply to you, but it's something to keep in mind as you shop:
We tow with a 2017 F350 CC DRW 4x4 with an 8' box AND I use a slider hitch!
Why? Short version - Our 2018 Raptor has two front compartments with swing up doors for the 2 propane bottles and the 5500 generator. These can NOT be fully accessed when the trailer is hooked up. We also commonly stop along the road for the night - I want to be able to check the generator, have access to the gas bottles without un-hooking (like in a rest stop). An RV tailgate would not solve this issue.
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Additionally, with a normal tailgate and a normal hitch, you must back up very straight to connect while the tailgate is down. Yes, I could get the pin box inside the bed, then close the tailgate, but the odds of destroying the tailgate go up significantly. Lastly, forget about getting much of anything out of the back of the truck when connected to the trailer with a normal hitch.
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A fifth wheel tailgate wouldn't fix the issue. A new longer pin box that fit and was approved by Keystone is not available. If I wanted to get those compartments open while hooked up, I needed a 12" slider hitch - I picked a Kurt A20 tube slider that is compatible with the trailers Rota-Flex pin box.
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The sliding hitch now gives me full access to both compartments even when hooked up.
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Now there is plenty of room to access compartments and/or get things out of the back of the truck.
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Lastly, we love this rig. I had enough capacity that I could safely add a 90 gallon auxillary tank/tool box.
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Many (most?) users might say this is foolish. But I wanted access to those front compartments at all times! I love the extra space between the truck & trailer when extended, and I had plenty of capacity for weight and size. So, that's why.
Those front compartments are just an issue to keep in the back of your mind.
Good luck with your shopping!