Hi @Ryan-D
You can dynamically pass the choice field value to "Search for users (V2)" action:

Next, pass the email address from the output of previous action in the approval process as shown below. When you pass the email address, the flow will automatically wrap this action in a loop(Apply to each):

OR
you could create a custom sharepoint list that holds the approver name & its email address in 2 separate fields. Using "Get items" and apply filter query, you could get the email address of the approver from that list which can be passed to approval action.
If this helps & solves your problem, please remember to give a 👍 and accept my solution as it will help others in the future.