Using OAuth 2.0 machine2machine

Hello everyone,
I’m doing integration between Jira and Service Now, and I have to use OAuth 2.0 as authentication.

I’ve read the following doc OAuth and it looks like there is an integration only with OAuth and it needs user input to work.
My first question is: this “user input” it’s something done one time, or there are cases where this could be requested again?

I’ve also read that there is a different way to do it: Configure an outgoing link | Administering Jira applications Data Center and Server 9.2 | Atlassian Documentation

Just reading the doc looks like I can use this element for the integration, but I’m not sure if this will require user input (and if yes, for how many times). Anyone have used it before?

Can someone give me some info?

Thanks a lot,