What WH do you have?
As for tankless WHs. I have one at home, it took a bit to get use to. I would NEVER have one in a tt, unless we changed our camping style.
What style camping do you do? If you boondock you may not like it. For example, everytime you turn off the water, the heater shutdown. When you turn on the faucet, the safeties require a moment to purge the flame chamber before ignition. This allows a slug of cold water to be passed through. This is not nice if taking a navy shower. You can also waste a lot of water taking showers or dishes, if you want hot water.
Now if you camp with full hookups, this cycling usually is not a big deal.
2012 Jayco X23B
2020 Ram Laramie 3500 SRW Air ride 50Gal fuel tank.
2007 Dodge Dakota Quad Cab (retired from towing)
Equal-I-zer 4-Point Sway Control