@JazzyN20 yea for final solution when list will have 1000 items, you should put a filter query o Group ID
So first you will need to identify the users from AD group which are not added to SharePoint list, to do that follow below steps:
1. Add select action after Get Items, and configure it as below screenshot, for From parameter select value (list of items) from Get Items dynamic content and for Map parameter, click on little icon on right of the input box, instead of Title column you can use the column which stores email of user in the list

2. Again add select action, and configure it as below screenshot, for From parameter select Group Members from dynamic content and for Map parameter, click on little icon on right of the input box and select Group Member Mail

3. Now add filter array action and select the second Select (group members) output in the From parameter, then in left side of value use join(body('Select'), ';') expression, select does not contain from dropdown and on right side of value user item() expression as shown in below screenshot

Now you will have array of list of users (email) which are added to AD group but not added to SharePoint list
to add the remaining users to the SharePoint list configure apply to each and create item action as below screenshot:
