I know you have no ethernet on the MBPr but if you have another computer with ethernet .. windows is fine as you can run airport utility 5.6 on that.
Or buy a usb to ethernet or thunderbolt to ethernet dongle.. which is fairly cheap now.
Setting up wireless by wireless I always considered to be the definition of frustration.
The moment you make a change the change stops the connection from working to make any further changes necessary.. so you have to get it right the first time.
It also depends on how you intend to set this up. I think you are in the Europe.. Does your ISP use PPPoE ??
If not you are forced to use the modem as a router and the TC has to be in bridge mode. If the ISP support PPPoE then you can bridge the modem and use pppoe in the TC wan setup.
I will show you the bridge setup as that is the easiest to get working.
So plug the TC into the TP-Link by ethernet. Do the factory reset on the TC again.
Open the airport utility and simply change the TC to bridge mode.
Don't change anything else.. update the TC.
Now when the TC comes up link to it again.. the internet should work as well as giving you access to the TC hard disk.
You now need to fix up the wireless. You can do this in several different ways.. since you have a wireless modem router.. decide which is required for wireless.. perhaps turn off wireless in the modem or the TC.. this option 1. That is the easiest and makes things simple.
Option 2. Use roaming network. http://support.apple.com/kb/HT4260
Although you have two different routers it will setup the same as two apple router.
I would probably use manual wireless for 2.4ghz .. select one of the channels, out of 1, 6, 11 or 13 for TP-Link and pick one of the remaining for the TC.
Option 3. Two different wireless networks with different names.. this is also fine although fixed channels is still good.
If you use 2 or 3 keep the two routers separated by a couple of Meters. That is just for wireless Tx not to swamp wireless Rx on the adjacent router.
If you have issues.. tell us where specifically you run into trouble.