Stephen has some good explanation of the types of links, but let me add some more information that may help answer your question.
Affect on SEO
After reading your article source, I don't think the article you reference has anything to do with your migration. The article is more about should I use absolute or should I use relative URLs? At the conclusion of the article it states:
From an SEO point of view, the most important thing is that the URL
points to the correct point on the server.
There is no perfect solution to which URLs to use on the site. Both
relative and absolute paths have pros and cons. Relative paths make
the developer’s job easier and faster.
I also think this article is probably more important for those who write raw html files rather than those who use tools like WP. People who code raw html are faced with this question every time they write code. I've never thought about it once in the 5 years I've used WP, but always thought about it when I was writing code with a text editor. (I can't speak for Joomla as I've never used it.)
How WP writes URLs and its impact on migration from staging to production
As I mentioned in a previous edit, WP writes all URLs as an absolute URL in the final page (assuming your didn't write the URL in the text editor). However, it pulls these URLs from the database and adjusts the host to match the host set in the WP configuration, which is helpful when moving from staging to production. I.e, dev.example.com to www.example.com. There are also tools to help migrate WP content between two hosts.
There are also several plugins and themes in WP that will automatically create canonical links preventing the theft of content the article refers to. This eliminates one argument for not using relative URLs IMO. If you don't want to use a plugin, you can always code it in your child theme.
What to do if you're worried about 404 errors due to migration
I would suggest you look at a tool that will scan your entire website for internal 404 errors. Screaming Frog and others can do this for you. Using the results, look to see if the migration caused any broken URLs. Then you can decide if you really need to take the time (and risk) to modify your existing URLs.