@rc4401 

Yes, you will be able to do that.

As a side note, if the Deco is in AP Mode you can have more then one Deco wired to the main router. In Router Mode only one Deco is to be wired to the router.

@Tony 

Can you explain the advantage of all 3 connected as AP MODE (ac points ) or  ROUTER MODE one connected with 2 and 3  ?

I was thinking of the the ROUTER MODE - 

ISP >  M5 ( port 1)   #1

           M5 (port 2)  >  tp-link (TL-SG105)  IN  (port 1)   --
                                                                       (port 2 ) out - M5 (port 1) #2 in 
                                                                                              M5 (port 2) #2 out to TV

                                                                        (port 3) out - M5 (port 1) #3  in 

                                                                                             M5 (port 2) #3 future use
Will this give the best stable wifi and tv streaming? Is the ethernet backhaul the best case if possble?

@71charger 

Wired is always the best connection so if you can wire the entire Deco network that gives the best speed and signal. What you showed as the topology looks good.

In looking at Router Mode vs AP Mode.

Router Mode gives you all the features the Deco has to offer, in AP Mode you lose most features. However, in router mode, all satellite units need to connect behind the main Deco. In AP Mode, you can actually wire multiple Deco units directly to the main router (non-Deco).

More info on AP Mode: https://www.tp-link.com/us/support/faq/1842/

Article that talk about Router Mode vs AP Mode: https://www.tp-link.com/us/support/faq/2399/

@Tony 
I have it all connected as outlined and it is working great so far. 

I have top internet  everywhere in house on both floors,  and the patio connection as well (with added benefit of reaching my external garage that is 40 feet away)

Thanks for the information.

@71charger 

Very welcome.