Hi @TerjeMonsen,
I would suggest to have a look at the except method described by @DamoBird365 in one of his blogs:
https://www.damobird365.com/efficien-union-except-and-intersect-great-method/
Within this approach you could use the outputs of the two actions a filter if an item is not available.
Below is an example of that approach for your setup
1. Switch both Map fields to text mode with the button on the right side. This makes it easier to compare
2. Add two Filter Array actions. The first one will check for new group members. The second one will check which ones have been removed.
Below are the expressions
From - New group members
body('Select_Email_from_Group_Members')
Criteria - New group members
@not(contains(body('Select_Email_from_SharePoint_List'), item()))
From - Missing group members
body('Select_Email_from_SharePoint_List')
Criteria - Missing group members
@not(contains(body('Select_Email_from_Group_Members'), item()))

Alternatively, you could just delete all items from the list and just add the group members to the list. That would also work. Unless you have a specific requirement to keep track of changes and history.