When you say Meraki-Meraki, do you mean two MX within the same organization using AutoVPN, or do you mean as third party VPN peers?
If you mean third party VPN, then it doesn't matter what model is at the other end of your tunnel.
Event-log wise, I'm only seeing single phase 2 negotiations on the tunnels I'm reviewing. Not like an ASA where you get a child policy for every subnet.
What are you trying to do?