Blackstone Ranch Goat Soap review for REZ Preorder, Back In Stock

I cant figure out how to set it to where the customer gets notified before following through with a purchase with mixed carts. I also dont like the thought of the customer being charged twice for shipping unless they wanna wait for everything they ordered. I think for now, the notify me is good enough and i really like that feature since i make cold process soap and it takes a few weeks to cure