I don’t understand the connection, but yes.
use an acf/save_post action. Check the $post_id in this function to see if it is a user or a post that’s being updated. I would test to make sure it’s the right post type as well if it’s a post. Get value from the notes field that’s being updated, look up the other side, either the user or the post, and update the field for the other one. The biggest problem will be with updating posts. You’ll need to do a query to get a list of posts that match the user id and then loop through all of those posts and update the field for each one, even if that is only 1 post.
