Here are a couple of tables which summarise the most important features of different types of copies, clones, links and aliases used in Mojave running on APFS (with a little reference to HFS+ too).

The first shows succinctly how to create each type, according to whether you want it to point to individual files or folders, and whether you are sticking to the Finder and GUI or working in Terminal’s command line.

The second summarises the main properties and usage of each of those types, which should help you decide which is most appropriate for particular applications.

I hope that you find those useful. As they contain quite a lot of information, I may well have left some minor errors in them. If you do see anything which is either wrong or needs improvement, please let me know in a comment and I will update the table.

(First version of 8 January 2019.)