I see in the instructions, "when IPTV is configured, the other port of the main deco can only be used to support the IPTV service." 

1. I'm not using IPTV, but my ISP does require VLAN tagging. How does the IPTV limitation affect me?
2. "THE other port"... I have a Deco X55 with 3 ports. Does this limitation only affect my port #2 on the main unit, or does it affect ports 2 and 3?

I'm guessing that a technical person would phrase the limitation as something like, "If you enable VLAN tagging, ports 1 and 2 will be on the VLAN and port 3 will be on the home network with the WiFi and the Ethernet ports on the other units."   Is that an accurate characterization?