I can attest to both of those things. They both happen to be $15, which I think is a fair bit cheaper than the official versions?
Sometimes my mayflash gamecube adapter reads the analog sticks wrong when the system comes out of standby, but just unplugging and replugging the offending controller fixes it
I have an amazon basics usb 3 network adapter, it works fine. The cord is too short for the back of the dock to close though.