Do I need an on board generator?

I would, the fridge takes a fair bit of power on its own, then in you plan on using the air fryer/convection microwave, that's a huge electrical load.  I hat the trend that manufactures are going with solar and LiFePO4 batteries, there is no reason they could not have fit the 400Ah of lithium batteries in the original battery compartment, but that would entail then buying a different brand that makes a reasonable sized battery.  

take the Cirius 920 for example, they brought it back and I was anxious to see it as it would be the only model that would fit on a long box they have and I like the Alde combi heat system, so I was interested in it.  the went LifePO4 and solar and changed everything into it to electric, stove, fridge, oven heat water, everything..  they went to 810ah of LiFePO4, 930 watts of solar, but they used the stick on ones that will need to be replaced after 10 years instead of residential panels that would probably last over 30 years. so with the electric alde hot water and heat, the 2 burner induction stove, electric oven , microwave and they sell it as a boondocking monster..  talking with people who have bought it, you can go a normal weekend with out plugging in, longer if you don't use the interior appliances or hot water.  so for anything over a weekend it is a plugin campground queen.  

now for you, I would just buy something like a nice quiet honda, if you are not worried about running the AC and just want an emergency charging method, then get a 1100i , if you want to run the ac then one bigger..  then you can keep it in a storage compartment and pull it out when you need it.  

the other option is to install a dc to dc charger and run power wires from it to your truck.  then if you need to you can use your truck as a genny and you don't have to spend that amount of money or give up the space to carry a genny.