You can absolutely start Wi-Fi-only, and plenty of people never add a hub. A hub becomes useful once you want devices to talk to each other (like a sensor triggering a light) or want local control that doesn't depend on the cloud.

Both are low-power mesh protocols built for smart home devices rather than raw speed. Z-Wave uses a single regulated frequency and tends to have less interference; Zigbee is more widely adopted and usually cheaper, with a bigger device selection.

Yes, increasingly so. Matter is designed to let devices from different brands work with different hubs and voice assistants without proprietary bridges. Support is still uneven across older devices, but new products are adopting it quickly.

It varies a lot by brand more than price point. The bigger risk isn't the hardware itself, it's whether the manufacturer keeps shipping firmware and security updates. A device that's stopped receiving updates is the real red flag.

Router firmware updates, a change in Wi-Fi channel, or a hub app update are the most common culprits. Before assuming the device is broken, check whether anything else on your network changed around the same time.