The "combination Modem / Router" needs only one cable. I would configure that modem as "Bridge mode". It might still have a private IP like 192.168.0.1 but that will get irrelevant if you're using PPPoE (which I recommend). If you have a second subnet out there in the WAN-routers it will be more difficult (if at all possible) to route port forwardings and it adds one inneccessary hop. So if possible for you. I'd rather use two dumb DSL modems (or the thing in bridge mode) that separate routers with separate IP subnets.

Then what does the "Charter cable" do? Deliver your LAN to somewhere else? Then you'd need to plug it in your switch. If it's supposed to be a third WAN, you need to plug it n the third WAN outlet and configure your TL-R470T+ accordingly..

Thanks so much Ande for input on my situation. I am sure this would help most people but unfortunately I am not among them. You obviously did not read this in my thread, " Secondly, Please provide STEP BY STEP instructions as to how to configure
the software to perform as indicated (I certainly would appreciate any
screenshots along with the instructions). Please, please understand that I
have NO EXPERIENCE AT ALL in doing what I desire so please be very specific." but I honestly appreciate your attempt to help me.

I did read your entire post but I am not working for TP-Link and I only have a limited time to do unpaid "service". Arxt I do not know your other routers, you didn't let us know what the charter cable means. Under these conditions, I suggest you find someone who could come to your home and configure everything, maybe on Craigslist if there are no other options.

What you are asking here has to be compared to repairng a motor. If you don't like to open your hood and get your hands dirty, please seek a workshop. :-)