RP-AC68U setup advice please

I have just connected an RP-AC68U on my network. I connected it via an ethernet cable and set the repeater to AP mode.

Could I ask if I need to set the wires settings the same as for the main router i.e. the same control channels the same band width etc

I have set the SSIDs the same on RP as the router. Roaming assistant is enabled on the router. Does this also need to be enable on the RP?

Many thanks guys.