I generally agree with the 2000 watt inverter suggestions, but I also think you could get by with a 1500 watt.
I think you have greatly overestimated your loads.
Your "critical load", instead of 864 watt hours per day, might be closer to 250. Link
2 phones 10 watt hours
2 tablets 60 watt...
Can't help you, but would like to ask why you are switching. I just bought a 2812, having had great success with Magnum inverters for many years. But I haven't installed the new one yet. Wondering if their quality has declined over the years?
Here are some thoughts on 12 volts versus 24 volts.
For any given amount of power (watts) the amperage will increase as the voltage decreases. For example, 240 watts at 12 volts is 20 amps, but 240 watts at 24 volts is just 10 amps. This is important because electrical wire is rated with...
A single 100 amp hour 12 volt battery has about 1200 watt-hours of energy, so each one is about what you need to refill two of your 500 amp hour bike batteries.
You could use a single 400 watt solar panel to charge your 100 ah battery during the day, and then use your battery+inverter to charge...