If you want to go the Ethernet backhaul router, connect one Deco to the internet router, then connect the switch behind it, then have the other two Deco units wired to the switch.

router > Deco > switch > 2 Decos

Here is a FAQ that shows the star topology: https://www.tp-link.com/us/support/faq/1794/

If you set it up that way what speeds do you get?

@Sal Turn you Deco units into AccessPoint mode, in the Advanced settings.

@Tony I have exactly that setup that you suggested, when doing the speedtest while connected to the main unit, all is good but when connected to the slaves there is a drop from 350 to 90'ish eventhough they are wired.  All are v1 models.

If i get a M9 as main, will it fix this or a m5 v2?

thanks,

@Juansa 

I would get a computer, and then test the Ethernet cable at each point to see if there may be a point where the speed drops. 

For example, take the cable that comes from the Main M5 and test that speed, take the cable that goes into the satellite unit and test from that point.