We have the ONT in the living room, also the Fritz!Box 7490 as the Modem and Router, at one end of our house, make the Wifi signal tricky on the other side of the house. It's never bother myself enough as my PC is using Ethernet cable and the Living room TV as well. When we got the Fritz!Box, the Wifi is not that Stellar, and to cover a new TV in the living room streaming internet content I just got a TP-Link Wifi extender,without doing any research at all, not my brightest moment. Now we do got 5G Wifi signal in the other end of the house, 2.4G is weak, but still fine without the extender, but still the iPad and Phone keep losing Wifi signal from time to time. I think the issue likely due to the extender not 100% compatible with Fritz!Box, so it create a separate set of Wifi channels competing with Fritz!Box's own channels.
As my broadband contract expire soon, I am considering got a decent all in one router (Huawei HG659 or preferably the Skinny/Spark one) to have good enough Wifi to cover the house, still plan to keep the router/modem at the living room to minimize change and probably get rid of the Wifi extender. As we are on Fiber 100 plan, is it a reasonable plan to use a single router/modem to cover the whole house with 2-4 adults?