Reinstall necessary on major macOS update?

I'm new to macOS and I try to figure out things before a planned set-up.

If one configures Mojave and he wants to upgrade to some newer milestone in e.g 2 years, is this possible via built-in upgrade or is a fresh new install necessary?

Or in other words: when do I have to follow this guide https://www.tonymacx86.com/threads/update-directly-to-macos-mojave.260654/ and when a simple update via macOS' built-in features is possible?

submitted by /u/KKK543
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