Shared folder on external drive
My Mac mini has an internal drive of 512 GB. This is not enough for all the user data as my wife and I have accumulated a lot of photos and videos over the years. I decided to move both of our Photos and iMovie libraries to the external drive in folders specific to our users. I limited the permissions of both users to their respective user folders on this external drive. Basically, I modelled this after the permissions set on the users folders that macOS creates by default. This is working fine, but of course I had to turn off "Ignore ownership on this volume" to get this to work.
I also created a folder that should be a shared folder between the two of us. I am wondering how I should set the permissions in such a way that both my wife and I can read and write to files. Normal behaviour is that only the owner can read and write and other users can only read. At least according to Apple and some other articles I found.
This answer on StackExchange uses access control entries, which I am not really familiar with, but is quite old. Furthermore, it does not work for files moved into the shared directory, which would happen occasionally.
I also noticed that the umask is set to 0022. Would it be an option to set it to 0002? I think this should solve the sharing, as groups would have read and write by default. Would this break other stuff in macOS or make things less secure?
What would be the best option to properly set this up?
By the way, I have a Mac mini 2018 still running macOS Catalina (10.15.7) although I am planning to upgrade it to Big Sur at some point. I assume this does not really matter for the answer to this question.
Mac mini, macOS 10.15