A few have already put it out there, but the best approach for us is all of the above. Every camper we've ever owned, the first thing I've done is add a 2nd battery. Some prefer the 6V GC batteries, others (me) the 12V deep cycle. Just a preference for me. Both have pros and cons. We've never been really serious about solar until now, but when the new Toy Hauler comes in, I'm installing
100W MC or maybe the 200W version as a hard mount on the roof. This is ONLY to keep the batteries topped off. While we haven't done a whole lot of dry camping, it'll be nice to have something providing a quality charge when we're out riding the motorcycle or on the bikes. Since we bought our first camper 15 yrs ago, Solar has dropped in price dramatically. A couple hundred watts was in the $600+ range and the controllers cooked your batteries if you weren't VERY careful. Now it's doable for half that and the system as a whole is much more reliable and safe on a variety of battery types. The jumper cable method works in a pinch, but they tend to work a deep cycle battery pretty hard charging them that quickly. Regardless of which method you choose, get in the habit of checking the water levels in your batteries regularly. Every couple weeks while charging until you get an idea of what your batteries are doing. And keep a gallon of distilled water handy for them. Most modern charge systems do a pretty good job of going into a trickle or float mode when the batteries are charged, but once the plates have boiled dry in any cell, the battery is toast.
As a final addition, the new TH gets a generator rack on the tongue. Most of our camping is in the Colorado mountains where AC isn't needed much in the day and it cools down nicely at night. But for those occasions when we're in Moab or lower elevations in the summer without hookups, it's almost a necessity to have AC. Some of the places we camp and play, it doesn't even cool down much at night. There's no way I'm filling the pass through storage with enough batteries and the roof with enough solar panels to run an inverter and the AC. So the generator WILL be on board.
Like everything else here, you have to find what works for your style of camping and your needs and set up your unit accordingly. I would STRONGLY discourage you from unhooking any of the propane, CO, or smoke detectors. They're there for a reason. You can overcome their minimal drain pretty easily with just a couple small tweaks.
Last but not least.......post some pics of what and how you do it.