Battery recomendations.....

On our 23ft TT we had two deep cycle RV/Marine batteries. This was before laptops, iPhone, iPads, Sat TV...etc so the two batteries would aloow us to camp for 3 days without the need for charging. As we added electronics and moved to a 38ft 5th wheel we found the need for 4 RV/Marine batteries plus a generator to charge them with daily.

I'm cheap so I haven't gone the 6Volt AGM battery route. Most RVers agree these are the best batteries for heavy use.

We get by with the 4 batteries, a 2000 watt inverter and a 2000watt Honda generator. Plus a second 2000watt honda in parallel when we need to use the air conditioner.

Using 110v TV and Sat box plus a laptop and charging iPhones and microwave for warming leftovers (up to 5 minutes). The Lights, water pump and refrig (on Propane) using 12 volts we can go for two days with some conservation (turn off lights and electronics when not needed) before needing to charge the batteries. But with normal use we need to charge daily for about 4 hours.

Hope this helps

It really depends on how And where you camp. If you stay at places with electricity most of the time a single interstate would work fine. If you get off the grid as I prefer then you need a lot better battery. I use two Trojan t105 six volt and even with heavy use my last set were still strong after eight years when they were stolen. Very high quality battery
Good luck / skip

Depends on what your needs are. If you dry camp then buy the batteries that offer the greatest amount of amp hours available. (6 or 12 volt) If you camp with hookups then no need to go expensive with batteries. We choose a pair of 6 volt golf cart batteries (Trojan) as we dry camp a lot. Good luck with your new rig!