@Dolanduck 

Hello Donlan,  So SmarConnect takes away all of the guess work from your network management.  It creates a unified SSID and password that both 2.4GHz and 5GHz access.  So when you turn it on, 5GHz isn't disappearing but rather you will only see one singular band.  When clients devices connect it the router will assign those clients to either 2.4 or 5GHZ.  This discision is based on client capabliities, range, and traffic needs.  MU-MIMO should remain active in a SmartConnect enviroment, but is a feature that is controled by the router. 

  @Carl well I wanted to know if the mu-mimo stays on in smartconnect mode And does not disable it. 
read somewhere where it disables it but I don't know if that's true. 

  @Dolanduck 

Yes I understand I realize my answer was long form but I wanted to explain the service as well as you mentioned 5GHz disappeared as well.  As far as I am aware SmartConnect does not disable MU-MIMO.