If we have a list of customers with 1000 profiles in it and create a flow triggered by that list, will everyone already on the list get the emails in that flow once it is set Live? Or will only profiles who trigger the flow after it is set to live trigger?
If you create a flow triggered by a list that already contains customer profiles, only customers who join the list after the flow is set to live will receive the emails automatically. If you want all profiles within the list prior to the creation of the flow to receive the emails, you must back-populate your flow using the 2nd option, "Schedule emails relative to when I click the back-populate button." Check out our article on back-population if you are not familiar with the process.