I am currently planning to buy a Raspberry Pi 0 for basic and portable office work (text and calc) and maybe read comics (in case it matters at all). The plan is to use a powerbank to power the computer and a regular 7 inch screen, but I am afraid of not understanding how electricity works and fucking it up. Both the Pi and the screen require 5 volts input.

If my understanding is correct, when choosing a powerbank voltage output matters more than Amps, is that so? I have the notion that it doesn't matter if the device I buy has a 20000mA capacity since modern devices can regulate the intake and use only the total 800mA needed, is that correct?

Also, would there be any advantage or change whatsoever by powering the screen through the Pi or directly from the bank?

Thanks in advance.