Do I want to book a plaza breakfast at 7:30 am I want to take advantage of the magic morning? seems like a early breakfast res would be better on a day without early entry.
You are correct, if you don’t have Magic Morning/early entry, breakfast is a great excuse to get in early by going to the turnstile dedicated to dining reservations, showing them your reservation & entering the park as early as the early entry crowd gets to go in. You can even do a few rides before your reservation time (assuming you get one later than 7:10).
But, if you have Magic Morning then better to save that Plaza Inn for 10ish when crowds start rolling in.