Sharing files between two users on iMac

I am getting ready to purchase a new IMac and want to make sure I set it up so that I don’t run into the issues I have today. My wife and I have a shared folder called ourstuff in /Users/Shared. However when one of us creates a new file in either that folder or other sub folders we don’t seem to have edit privileges without doing a get info on the user who created its ID a and change to RW for both of us. I am hoping I can setup better file sharing on new OS or is there something basic I am doing incorrectly.