A:AnswerSo, needing an external device is up to your service provider, there are many that run direct fiber to the home or business that will attach directly to the sfp+ port on this router without any extra equipment needed.
A:AnswerJust wifi 6, though you can add more ASUS routers to decrease congestion on a single 2.4ghz channel, or even wire some devices in for Ethernet backhaul to reduce your overall clients. This router supports 50 clients at once though. Hasn’t been an issue for my IoT smart home devices.