Unless you can fit 4000w of panels on your RV roof, it is probably unrealistic to ever leave both rooftop ACs running for very long, unless a generator or shore power were involved.
You can almost certainly run one of them basically 'for free' (supported mostly or entirely by solar, most of the time, during certain times of day) once you've maxed out your rooftop real estate with solar panels.
Even if running AC isn't your TOP priority i feel it should be addressed first because it's the most strenuous thing the system will probably do (not planning to run an electric clothes drier, are you?!) and also one of the things you might be the most let down about if you just assume it's going to work and it doesn't. So in my opinion, temper your expectations to run both units off solar. It probably can't happen unless you have 'deployable' solar you can lay on the ground. You can probably run one comfortably AFTER filling most of your roof with solar panels, and you can probably run both if you design the system in such a way that one can run off solar and the other can run for a short while off battery to cool the space before returning to a single unit running, or the other could run off generator or shore power instead of your solar/inverter/battery system.
If you EVER wanted to run both off of the inverter, you would need a pretty large inverter (such as a 5000w+) and would have to start them individually as their compressor startup surge is large enough that most single inverters other than the huge 12-15000w models, could not handle 2 at once, nor could your single battery. Starting them one at a time would get around it for a while.. because both compressors would run continuously at first. Once they get close to the temp setting and their compressors start 'cycling' on and off it becomes a crapshoot because there is always a chance they will both try to restart simultaneously and overload the system.
So you may just choose to never attempt to run both off of an inverter simultaneously, which would simplify your inverter shopping quite a bit. There are ways to wire things such that one of the the units could run from inverter, or generator, or shore, or only 2 of those, or only 1. Or, you could install a smaller window unit, or mini split, and only run the big rooftop units off shore power or to initially cool the space before switching to the smaller units. Up to you how you want to play that, eventually.
So, before you can go inverter shopping you need to decide "do i EVER intend to run both units off of an inverter, with full knowledge of the bag of issues i'd have to manage?". If yes, we can start talking about inverters that can do that. If no, we can start talking about some other inverters.
As far as which solar panels to buy.. 100w panels are typically '12v' panels which means you will be limited to using them in series strings of no less than 4. So unless you stop with the 2 you have and buy a particular 'voltage boost mppt' to run those two, and then switch to something else, you'd have to at
least pony up for 2 more matching panels before you could switch gears to buying other panels, if you wanted to. Reasons TO switch to larger panels: cheaper per watt, more likely to be found used at a heavy discount, less total wiring and mounting connections to make. Reasons NOT to run larger panels: Harder to maximize your roof utilization because big panels can only fit certain ways in certain spaces, smaller ones give more opportunities for "tetris" filling up all your empty spaces with panels.
Ok, i'll stop there until you answer that AC question.
