I put in 2 CAT6 wires to every room in the house (4 in my office, 4 in garage), with one big PoE switch in the garage.

Everything with an Ethernet port is wired, wifi is for phones and tablets only (a few UniFi WiFi 6 APS).

Works great!

Internet has never dropped for me while working, family loves the always working NAS streaming via wired Apple TV.

Not theory, this is literally just how it works. Only one device can transmit on a WiFi channel at any given moment. A whole lot of the WiFi standard is just dealing with scheduling multiple clients wanting to transmit on the same channel at the same time.

The more clients you have on the same channel, the less bandwidth they all get (effectively). Using wires where you can will improve wireless for everyone else, including your neighbors.

Incidentally I ran cat6 to a few locations but its so thick and stiff I kinda regret it. The internet seems to think 5a is more than enough and 6 was a waste.

I did this five years ago, and it's been great. My wired access points are still Wi-Fi 6 and I've got no inclination to upgrade them yet, connectivity has been near-bulletproof.