I'm not that knowledgeable on networking, but I do remember that if a device is connected to a wired network, it can end up receiving packets not meant for it because switches will flood all the ports for packets they don't know how to route. But I also heard that Wi-Fi is supposedly smarter than that and a device connected to it should never receive a packet not meant for it.

Is this true? And in practice, does this mean it's preferable should keep computers with invasive operating systems (which might decide to record foreign packets sent to it in its telemetry) on Wi-Fi instead of on the wired network?

Also, how exactly does Wi-Fi prevent devices from receiving the wrong packets when it's a radio based system and any suitable antenna can receive any Wi-Fi signal? Does each device get assigned a unique encryption key and so is only capable of decrypting packets meant for it? How secure is it actually?