Number of network sockets; how to plan Wi-Fi in the new building?

So a buddy, just to be safe, pulled Duplex CAT7 behind every mirror (including the hallway!)... in case smart mirrors ever take off.

Really, your toilet needs LAN too?

Yes, of course! My Japanese hi-fi toilet!

WLAN replaces LAN in 99% of cases. It runs just as fast and stable. Exception: gaming and TV with UHD etc.

Nobody installs a telephone socket in the rooms anymore either...

Sorry, but you obviously have no idea about the subject.

Wifi has less performance even with only one client than 1gbit lan! But there are always multiple clients in Wifi, so the performance is further reduced. There is no way around Lan plus sufficient APs if you want a future-proof network. Only the slow 2.4 ghz network has more range in Wifi. For fast 5 ghz Wifi you need several well-positioned APs... A Fritzbox is a jack of all trades but master of none. It is OK for the grandma who lives alone in the apartment but not to cover a single-family house with a family.

Wi-Fi replaces LAN in 99% of cases. It runs just as fast and stable. Exception: gaming and UHD TV etc.

People also don’t install telephone sockets in rooms anymore...

following situation:
Wife streams Grey's Anatomy in UHD on the TV.
Child 1 watches 4K YouTube on the phone
Child 2 Skypes on the iPad with a friend in Australia
Child 3 is on TS gaming a round of Fortnite on the laptop

The oven is currently downloading an update, 2 Alexas are humming away, and my four outdoor cameras nervously film passing sparrows, the two indoor cameras watch the cat suspiciously.

I enjoy the peace and want to game myself, and Steam starts the 10GB update.

Nothing happens in my house. Everyone is happy, I grab another beer and go pee again, then the game is downloaded and we can get started.

In your house the wife starts yelling because Dr. Slone begins to stutter, Child 1 suddenly only watches videos in 160p and shouts loudly "DADDY!!!", Child 2 only sees pixelated mush and jumps off the bed stubbornly heading to the basement to you, Child 3 throws his laptop against the wall as the ultimate rage quit, the oven reports an error and will no longer turn on because the firmware crashed.

And all just because you were too stingy to put some CAT7 in the wall?

I always say: the "cordless cables" offer in every way the worst ratio of price, performance, and allegedly lower effort.