The migration is going to start with 3 x 9300 models. later is going to completed with more boxes.
So I need they work together mixed for a while, maybe a year or two.
The 9300 models are 2 x 9300-48T & 1 x 9300-24UX this one is going to arrive in 4-6 weeks more.
When you order the 9300s, order them with IOS XE 16.9 as that is a long-lived release. Only go to something other than 16.9 if you need a specific feature that came in 16.10 or 16.11.
As far as interoperability, that should not be an issue.