@Brian_Boltzman 

.....and what if I place the switch before the deco, would that cause a problem?

The configuration would then be, router>network-cable>sg-105e switch>tv and deco in access mode.

  @Brian_Boltzman 

When Deco is in AP mode, it still supports IGMP snooping and the signal will pass through as well.

I think since AP mode does not support VLAN tags anymore, "decos do not have iptv support in access point mode" mainly said you could not separate the Internet date from IPTV data through one port. So the following configuration is no longer available:https://www.tp-link.com/en/support/faq/2421/