C is Meraki's AutoVPN, I've used both RED and AutoVPN for more than five years and they have similarities, I'd say the Meraki AutoVPN is more resilient, easier to use and slightly less configurable.  I prefer AutoVPN over RED.   D isn't an MX in my experience, a Cisco FirePower device running FTD is closer to an SG for more advanced features like that. ... View more