I've always had this question and this is the first group where I feel like I will get a relevant answer.
I've started doing Pop again after many years of not.

In my old life, I might save a harmony for the 2nd verse or even second chorus in some cases. Then there are those times when I want to hook the listener in right away and I throw everything at them from the start.
I know it depends on the song and is subjective--I've been listening to top 40 and I hear both being used. What do you do? Vocal harmonies was only one example. How do you know if you should save a little something in the production for the middle or near the end of the track--or hit them at 80 miles an hour from beat 1?
Appreciate any input