Blake, the Meraki stack I have is from my Meraki certification training and I use for all my work related activities. The MX64 is limited to only about 200MB of traffic, so I needed something faster connecting to my Arris cable modem which now gives me 500MB of speed. So that is why I went with the Netgear connecting to that and using that for family and friends wireless access. I connected to MX to one of the ports for that so that everything behind the MX stayed the same and kept running. The challenge now is that several of the devices connected to the Meraki now are on the 192.168.128. network while all my wireless and personal stuff is connecting to the Netgear 192.168.1. network.
As to your first question, no I have not set up any firewall rules on the MX so far. I am not a strong networking guy (a sales guy at heart) but would be happy to learn more. Pointers to how to do this are greatly appreciated.
Ken Mage