High Speed WiFi Range Extenders for Demanding Homes

Not necessarily. The extender's link to the router, radio configuration, interference and client device all influence the result.

It is a class label for a combined theoretical WiFi capacity across bands, not a guaranteed speed for one device or an internet plan.

Additional bands can provide more flexibility for client or backhaul traffic, but the benefit depends on the model design and router connection. Compare the supported bands and your environment.

No. It describes the Ethernet interface's link class; the broadband plan, router, extender path and connected device also constrain throughput.