Hello, I think I may need help expanding my home network.

I have 2 storeys to cover, and I am in a country where the buildings are built with reinforced concrete, so the WiFi signal has a hard time passing through walls, and ISPs offer adsl/vdsl which means that all available adsl modem/routers have internal routing function that can’t be disabled.

My needs are a switch for 2 desktops, 2 game consoles, an ethernet printer, a NAS, a Smart TV, and as for wireless, I’d love to have internet available everywhere for my (family’s) 2 laptops, 3 phones, tablets, handheld game consoles and a wireless printer (not the same printer as the ethernet printer).

All rooms have an ethernet point, so in case of a Deco, I can set it up to utilize ethernet backhaul.

My Modem/Router is TP-Link TD-W8970 v3 (latest firmware) who’s routing capabilities aren’t great, and I’m thinking that a Deco M5 (the triple pack) would help a lot with my WiFi coverage. But since I can’t disable the routing function on the TD-W8970, I’ll have to disable the excellent routing capabilities of Deco M5 and set it up at AP mode. Or should I keep it at Router mode, even though my modem also has routing enabled?

Right now I’m using my TD-W8970’s WiFi for the 1st floor (I actually have stable connection in just one room), two no-name switches, and a D-Link Access Point for the 2nd floor (which freezes and requires rebooting frequently, so I want to get rid of it). My wirelessly connected devices on the 1st floor with the TD-W8970 lose connection and the ability to connect to the TD-W8970, and the only solution is to disable/re-enable the wifi on the TD-W8970 or reboot the TD-W8970. It’s not a single client’s problem, because it happens many times a day, and while this is happening, every wirelessly connected device loses internet connectivity at the same time (can’t open websites, can’t open 192.168.1.1, can’t ping anything, they don't get disconnected from the SSID but if I manually disconnect them they can't reconnect until I reboot the wifi function or the whole TD-W8970).

I’ve seen that there are some compatibility issues with TP-Link and D-Link products as well as with some routers, so I’ll remove my D-Link AP and change my no-name switches, that I intend to replace with the TL-SG108E.

I believe that my problem could be that I'm overloading the routing capabilities of the TD-W8970 with the 25-30 devices, or something that has to do with WiFi routing on that device. I don't use any torrent apps so I don't have hundreds of connections on any client, or millions of packets per second, I'm sure I'm not overloading any buffer memory on the modem. It would be ideal to have a modem with no router, so I could rely on Deco M5, but that's not possible with any modem sold in my country. They all have router included that can't be turned off.

I use address reservation on my devices and leave DHCP ON for my guests on a higher range of the IPs in order to avoid conflicts.

Please advice me with the best solution for a network with TD-W8970 v3, Deco M5 v1 (x3) (already ordered but not yet received) and TL-SG108E v4 (x2, one for 1st floor, one for 2nd) - not ordered yet.

A professional’s opinion is to get a Cisco modem and Unify APs and cloud key, but that’s overkill for a home network and over my budget, so I’m asking here.