Alright, I’m probably going to make some people angry with this one.
I think your stack-up should be figured out BEFORE you start placement.
Not “we have a general idea.” Not “we’ll figure it out once we start routing.” Actually figured out.
You already know this decision is going to affect your impedance, routing, return paths, power distribution, board thickness… so why would you start placing components before you know what you’re designing on?