If your system is 24 volt build for that voltage, you have a better balance on the cells and also higher voltage means lower amps so you can use smaller wires and save money and easier to work with, capacity will be the same either way
Ecoflow is very expensive, you can do the same thing for less money. Let's get back to the original question
I know and I don't want to use it to do that. But that's not my original question.
As long as the inverter will take the starting amps required compressors are hard starts
If you are steady at the average of the quoted portion, assuming you meant watthours, then 100Ah at 12V nominal is 1.2kWh and 200W load would be ~6 hours tops; 300W load 4 hours max.
It costs essentially the same per watthour for ether a 12V or 24V battery. The 50 amp hours of a 24V is the same as the 100 amp hours of a 12V- both are ~1.2kWh.
Fridges can run (like mine does) on 55W but when they start a cooling cycle they can be a lot of watts for a second or two. My current fridge bumps the inverter readout occasionally to something I’m guessing is 1400W but it happens so fast you can’t really read it. In the next second or two it will go to ~200+ watts and down to ~85W and soon - minute or so- thereafter will be 55-65W running.