I’m trying to learn the implications of some of the choices in the settings of the SOHO MK3.
Regarding port numbers, does it matter which ones I choose? For example, to invoke HTTPS for secure web admin, does it matter which port number I choose instead of 443? People are choosing many different ones, but does it matter? Are there some that you should not pick? I looked here: List of TCP and UDP port numbers - Wikipedia
Does this mean anything in terms of what I should not do?
You can pick any port number, but it is good practise to avoid the most common ports to avoid using any port that is already in use. Anything above 1023 is usually a safe choice.
This article shares a list of common network ports.
From 0 to 1023 – well known ports assigned to common protocols and services
From 1024 to 49151 – registered ports assigned by ICANN to a specific service
From 49152 to 65 535 – dynamic (private, high) ports range from 49,152 to 65,535. Can be used by any service on an ad hoc basis. Ports are assigned when a session is established, and released when the session ends.
This article clearly explains the use of TCP/IP ports.