I have an Archer C80 router, RE200 and RE305 range extenders, if I want to create a onemesh network, do I have to connect both bands (2.4 and 5GHz) or either band is enough?

I have an Archer C80 router which supports Hidden SSID for Guest Networks. I was planning to procure range extender RE305, so would like to understand whether guest networks can be added into OneMesh,