As far as Zigbee goes…
You can’t really say “this manufacturer’s devices work” - you need to research each specific device. How to do that depends on which HA integration you’re using.
Z2M provides a handler for each device it supports, and there is a list you can use to check whether yours is one of them:
ZHA aims to support any device that implements Zigbee correctly (it’s surprising how many don’t), so it is more difficult to provide a list. You need to check the forum and the GitHub page to see which ones have issues.
There is a useful database of Zigbee products:
Zigbee is not good at long distances. The signal is very weak and easily blocked by walls etc. You need a lot of routing devices to pass messages from one point to another. In a building with lights and sockets this is not a problem - it’s how it’s designed to work - but it’s not the best protocol for passing messages between buildings - from the house to the garage, for example.
No. Zigbee is a mesh network and messages are passed from router to router until they reach the coordinator dongle. In fact the dongle should only be connecting directly with a handful of devices.