Hi there, 

I just bought a three Deco P9 pack, and connected them as follows:

Modem - - Main Deco P9 - - Slave Deco P9 1 - - Slave Deco P9 2

The thing is that, although I've got 600 Mbps as bandwidth, and  I obtain 200 Mbps (Down & Upload) on the two first Decos (Main & Slave 1) which is quite good, on the third Deco (Slave 2) I roughly get 50 Mbps. I have the three of them in router mode and situated the main deco in a corner of the house, the slave deco 1 in the center, and the slave deco 2 on another corner of the house, as the image below shows.

I would also like to know whether changing from router to ap mode would improve the speed, and what are the main differences in those modes. I would also like to know if there is the possibility of choosing only the WIFI 5Ghz rather than the 2.4Ghz. And what does fast roaming really does (I´ve got it turned off). Thank you in advance.