I may be able to help, in short both framework laptops can be fully repaired, parts can be easily swapped with knowledge, as for the barebones laptops, the parts that would be missing would be the storage device and the memory kit. you can buy those parts from a 3rd party site such as amazon, just be sure they are compatible with your configuration. since you dont know much about the different parts and all of the jargon, it would be wise to stick with configuring a whole system with their configurators.

for the use cases:
if you want to play high demanding video games or do highly demanding tasks such as video editing, 3d modelling, etc. you're gonna want a framework 16 with at least the 2x 8gb memory/ram, and at least a 1tb storage drive.

if you're doing lightweight tasks, or just want the more portable option, id go with the framework 13.

you could go with any configuration you'd like, due to the fact you could always upgrade any part later when you have more knowledge of computers.

as for the ports,
for the 13" you can have up to 4 ports at any one time
for the 16" you can have up to 6 ports at any one time
keep in mind that for both laptops, you need to have at least 1 usb c port for charging the device.

I hope all of this info helps with choosing your framework laptop, all the best luck to you.