Best way of having Pathauto based off node title, but not tied to it? Sorry for the poorly worded question, I'll try to better explain myself.

I'm swapping (not migrating) from WP to Drupal and I'm trying to replicate WP's URL feature. I want it to initially be based off the title of the node ("My First Blog Post" => "my-first-blog-post")

What I'm not wanting is Pathauto to be directly linked to the title, so I can update the title to something like "My First Blog Post (Updated 5/4/2017)" without having to worry about the URL changing. I want the URL to be easily editable if the need rises, I just don't want it tied to the title.

Would the best way just be to add an extra field, and manually enter a 'URL title' in there?
The contributed module Pathauto will provide you a setting to set your own alias urls in the add content page.

Suppose you are adding a content of type basic page (using node/add/page), at the bottom there will be an url path settings tab where you can uncheck the 'Generate automatic URL alias' option and set your own path alias for the page.