VLANs in the private household, okay, why not. And 10GBit/s switch, haja. What can the 2-wire copper DSL do?! Well, prepared for the future. I'm somehow old-style when I have a FritzBox and a 250Mbit/s VDSL...
It's not just about the internet. Many setups cause purely internal data traffic. A NAS or media server in the basement, Sat-over-IP, data backup, and whatever else one can think of.
I agree with you, going from "forgot network cables during construction" to a 10GBit network is a big jump. Not to mention the costs. But dismissing it completely as nonsense as long as no GBit internet arrives at the house is also exaggerated.
With our customers, I see network separations with VLANs, switches with 10gb/40gb, or storage with 16gb/s fiber optics, etc. But these are corporate customers who have to spend tens of thousands of euros just for the hardware. In a normal (today's) household, I see a 1gb switch with PoE as acceptable, plus a router (possibly with a modem) and a few access points.
VLANs also make sense for private use (IoT, cameras, children, work, guests, etc.).
This only works with managed switches.
CAT7 cables provide the possibility to upgrade to 10gb later on.
I would not skimp on the APs. Personally, I want fast 5ghz wifi with multiple SSIDs as comprehensively as possible.
It is always a question of one's own standards.
If your internet arrives in the basement, do it like this. You won’t have any latency problems. If you properly install the cat7 cables and cat6 sockets, you’ll have peace of mind for many years. Also with NAS, streaming, gaming, and so on simultaneously. What you could still google is the influence of a direct current line right next to a cat7 cable (when the photovoltaics come and the inverter is located in the basement). I don’t think there will be problems, but if there are, you’ll have to invest about 150-200 euros more in a fiber optic run. Also no big deal. Zyxel, UniFi have already been mentioned, the high-quality (metal housing) D-Links are also quite good. But since switches nowadays really don’t cost much anymore, you can’t go wrong. Meaning, if you currently have no idea why you need VLANs, just take cheap, unmanaged brand switches for about fifty and relax. Much more important is to do the cabling properly once. And even that can be done sufficiently well after 60 minutes of YouTube and a practice socket. You already have the basic understanding.
Addendum: Regarding the underfloor heating issue, I would drill as far as possible into a corner of the room. Preferably between an exterior wall and a load-bearing wall.