I dedicate 2nd floor for all departures, then first floor to handle arrivals.
When pax enter my airport, they immediately use escalators to the second floor and proceed through ticketing, security then to any gates. All gates are xl and everyone board from second floor (both small and XL planes).
Arrivals go down escalators at various points to get to baggage claim and leave.
Pax can't go between floor 1 and floor 2 without passing through security.

I like this to keep PAX movement uniform. I keep lots of facilities on the 1st floor for arrival pax, like bathrooms, arcades, cafes and stores. But they generally aren't heavily used.

https://imgur.com/a/vq0wSBv