Does Meraki MX security appliances have the ability to perform site to site VPN connection or allow access to another network location by blocking or allowing a MAC address instead of by the IP address or IP subnet?
Access Control for VPN connections is handled via IP addresses or subnets, not MAC Addresses.
That said, you can use MAC-based access control to restrict access to the Local Network included in AutoVPN. If not allowed, the client will be blocked at the local network level and prevented from accessing anything.