It doesn’t appear that it is possible to set product option defaults. Has anyone found a way to do this?
You are better off contacting Wix Support if you want to see if you can set defaults for your products in the Wix Stores app itself or read through the Wix Stores support pages.
https://support.wix.com/en/article/contacting-wix-support
https://support.wix.com/en/wix-stores/managing-products-and-collections
There is no default option for Wix Stores through code.
https://www.wix.com/corvid/reference/wix-stores.html
https://www.wix.com/corvid/reference/wix-stores-backend.html
Thanks GOS - I actually asked WIX support about this (who I generally find to be very unhelpful) and they said there is no way to do this.