@Gally45 

When you do initial configuration of your first Deco as Main Deco, connect it by Ethernet cable directly to ISP router. This is to avoid any issues with initial setup.

After initial configuration, when Deco starts and possibly updates its firmware, and you gained access to it in Deco app on smartphone - set Deco to operate in AP mode. After that, configure the rest of Decos according to the user manual, and you can move them anywhere you want, including Main Deco.

>I was wondering would it be possible if I turn the wifi off on the isp router and then to set up the primary deco through the switch in another room in the house through an ethernet port

Yes, it will work. That's how it is in my house. I disabled WiFi on ISP router, made no other changes on it, set Main Deco in AP mode and moved it away from the router.

>for the the other two deco to be set up in ap mode also from ports in other rooms that feed back through the switch

This will work, too. One of my Satellite Deco is wired to a different port of a different switch, and another is on WiFi. Both work just fine.

>Ideally I dont want to have to put the primary deco in the plant room beside the router just wondering if this is possible.

Yes, no problem in AP mode. This is how my Main Deco connected to ISP router:

ISP router<--Ethernet-->switch1<--Ethernet-->switch2<--Ethernet-->Main Deco

>Also if I wire the decos will the second port on the decos work to connect to a smart lg tv or computer? 

Yes, it will. In fact, this how my Smart TV is connected now after I deployed Deco mesh:

ISP router<--Ethernet-->switch1<--Ethernet-->switch2<--Ethernet-->Main Deco<--Ethernet-->Smart TV

Does not have to be Main Deco, of course, Satellite can do just fine, too. Think of two networking ports on Deco as two-port switch.