John, my teardrop has LED lighting throughout, Small case fans for ventilation (very low draw), charging ports for electronic gadgets and a 35L Alpicool 12v fridge.
Obviously the fridge is the demanding appliance. In tests run in 2019 after purchase I monitored it for 58 hours after pre-cooling on 115v. It used 33.9 aHrs in that period with ambient temps at around 70f during the day and mid 50s during the night. That's under 14 aHrs per day. From Cosmo's comments his Dometic 35L has similar power draw.
I have 200 watts of panels (two 100w Renogy) mounted flat on my TD roof, a decent MPPT charge controller and 144 aHr battery bank (AGM). I've never had less than 12.5 v showing on my MPPT for battery level (I'm very conservative in my power use while camping). I went with MPPT as I wanted to mount my panels "permanently" on the roof and the MPPT will generate a smidge more amps that way. Even on a cloudy day I can look at the charge controller and see in the morning that it is beginning to trickle charge the batteries before noon.
Look into a larger, newer PV panel. A new 200w panel is smaller than my two 100w panels. Make sure you pick a charge controller to match its output (I am not an expert to help there). If you go with an inverter for 115v power you will have to ramp up your system. I find no reason to use 115v appliances.
NOCO makes some seriously good chargers for when you are in a pinch and have shore power. I chose a Genius 7200 (7.2a) because I have multiple uses for it at home. A 3500 (3.5a) would be enough for most teardrops I would think.
As far as my Alpicool 35L here is a link to the page where I detail the power usage and one or two minor problems which I easily fixed...
http://tnttt.com/viewtopic.php?f=2&t=71874&start=60Can't help with the DC to DC charging. Don't know enough about that and have seen too many posts about critical mistakes that can be made wiring it up. I'm satisfied with solar. Battery bank is going on 6 years old (eight 35aHr Mighty Max AGM batteries) and holding a very good charge. I would definitely go with AGMs again if they fail. In the winter my TD sits in a garage. I dismount one 100w PV panel and put it on a saw horse in the yard next to the garage and hook it up to the TD. Five winters doing this and not any problems (N. Wisconsin).