We start by making a list of all the loads we want to power, and the energy requirements they have. You need to know the difference between energy (watt-hours) and power (watts).
They are confusing you with different terms. Standard marketing ploy.
The "Amp-hour" spec you are reading is an attempt to give you energy capacity, but it needs a voltage to be useful information!
To get from amp-hours to watt-hours, multiply by volts.
For instance the $220 Jackery 240 is 16.8 amp-hours, at 14.4 volts - you multiply the two and get 242 watt-hours. So about 90 cents a watt-hour. Higher than I'd like to see, but typical for these "portable power stations" which are rip-off-y.
By contrast, the $50 Anker 325 has 20,000 milliamp-hours, which is a fancy way of saying 20 amp-hours. However, that spec is at only 3.5 volts. That means it actually has 70 watt-hours. That's 70 cents a watt-hour, which is better value but doesn't power anything but USB devices.
The Jackery can power small 120 volt AC loads as its power (watts) is limited... but only for a short time as its energy (watt-hours) is very limited.
VanLife really needs a bigger system.
Really, unless you're choosing to live like a homeless person, #VanLife calls for a proper, permanently installed 12V or 24V DC accommodation battery and solar system on the vehicle, powering all the living-space lighting and equipment. You don't want to sap the engine starting battery for those loads, because after a long boondock you might find you can't start the engine! 12 volt is easier to work with, honestly. And then you can get USB power off that battery system, as well as a large enough inverter to actually run refrigerator, microwave and the like. It can also provide power for very low-power fuel heaters such as the Dickenson.
This is more money than you are planning, but not a whole lot more, and you can do it in increments - get the battery now, then wire a cross-connection so it charges off the engine (but doesn't sap the starting battery), then get an inverter to run fridge etc., then add more battery capacity, then add solar, etc. You don't have to do the whole system in one go. You do need the skill to design a system, but info about that is all over the web.
By the way, 12/24V to 120V inverters are sold at every truck stop - Pilot, Flying J, Petro, that kind of place.
And getting from 12 volts DC to 5 volts USB is super easy - the adapters are sold at every gas station, convenience store, big-box and cell phone shop. In the US, they are easier to find than eggs.