I do something similar but use Samsung T5 and T7 drives for my working files and then archive projects to a pair of hard drives that are accessed through an OWC dock which mounts two hard drives simultaneously. I prefer standalone SSDs and have a dozen or so of the Samsungs which are small and convenient and have proven reliable. Keep in mind one HDD isn’t a secure long term storage solution because drives fail. Also, note that a dock or drive enclosure is another point of failure (this is why I prefer the standalone SSDs). I’ve had both HDDs and enclosures/docks fail. So far so good on SSDs (fingers crossed). My method is not the platonic ideal, I know, but it’s a workable solution for me.