Thats quite interesting. I noted I can't move its allocated channels on the 5Ghz band (I guessed due to its bandwidth needs) and thought it was spec'ed as a 4x4 MIMO AC2500 device - in other words 800Mbps 2.4Ghz and 2700Mbps at 5Ghz. That still leaves loads of bandwidth for backbone over 5Ghz but I'm intrigued if it uses dual 5Ghz bands to split out backbone traffic.
Can you point me at a source of information around this?
Whole Home Wi-Fi is a dual-band device - 2.4GHz is a 4x4 800Mbps radio and 5GHz is a 4x4 1733Mbps radio which takes it to 2533Mbps combined. If both backbone and clients are using the same band, the radio is shared.
BT claim that the Whole Home system works with any router/modem.
If I have a TP-Link 2800 with a guest network setup, how does the BT solution present this? Or does it ignore any guest network set on the main router?
To the best of my knowledge BT have not made public the details of the second 5Ghz channel however some of the reviews have mentioned the use of the channel to reduce contention. The Linksys Velop advertises itself as a tri band system as does the Netgear Orbi and I believe the technique is the same for for the BT system.
You could try the help desk but they probably do not have the details
If you follow the BT guideline you will turn off wifi on your TP link router to prevent interference and hence will lose the Guest network. However you can leave it running if you want although you may need to change the channel number.
