Main source for this: Mac beginner's guide by ETS – This whole guide is a blatant copy & paste, I deserve zero credits!
This guide mostly assumes a primary SSD and an external SSD, formatted as APFS. If you want to follow the commands verbatim, name your external SSD volume as ord-dev. You'll still need ~100 GB free on your internal disk, as only the bitcoin blocks are moved to the external SSD. This configuration allows for moving the bulk of the storage needs to the external but leaving enough in the default locations to make commands easier.