Hi all, my three-storey home is currently equipped with a 5+ year old Linksys Velop 3-unit wired-backhaul system, and recently I've noticed some lag if one device is streaming video and another is in a video meeting/gaming. I've since been doing some research to try to improve this and to take advantage of wifi6.

My house is concrete-built and has no existing ethernet wiring within. My current setup is basically the modem + Velop on the third floor where the gigabit fiber comes in (don't know why they did it on the third floor). I then have ethernet wires going down the stairs to the 2nd floor Velop, which then daisy chains to the ground floor Velop.

After much reading on here I believe most recommend a router + AP setup nowadays, and that's what I am planning to do with TP-Link Omada. I'm wondering if the proposed setup below makes sense?

1) Pull an ethernet wire from 3rd floor modem to 2nd floor, where I will have the Omada ER-605 router and controller. 
2) From the 2nd floor router, link it to an EAP610 beside it, on the 3rd floor, and on the ground floor using existing cables along the stairs.
3) Since there are no wires in the ceilings, I'm thinking of just mounting the APs on the wall or resting it above a cabinet.
4) Maybe add an injector for the ground floor AP, so it can directly flow from the ceiling of the stairs to the wall beside the stairs without need for additional power cable.

Does the above concept make sense? Would I require a switch? Appreciate any input. Thanks a lot!