what happens to the data I’ve entered into the field for these pages if I change the location rule to display on posts instead of pages? Is this data still taking space up on the database?
Yes, the data that was added for posts will still be there.
Do I have to delete all the field information from the pages before changing the rule so I don’t end up with data I don’t want in the database?
Deleting what’s in all the fields first won’t do anything except remove the content. The empty content will still be in the database. There isn’t any way to delete the fields completely when you change the locations except to go into the database and do it manually.
It’s a good idea to plan the development of a site so that once data is entered it does not need to be removed. I think there is a plugin that will convert the post type of a post in WP, in this case you could change your pages to posts and data in the fields will go with it.
