See: https://help.mikrotik.com/docs/display/ROS/Basic+VLAN+switching#BasicVLANswitching-Otherdeviceswithabuilt-inswitchchip for use with the RB450Gx4
In General, see: http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1
a unify AP gets configured via its own LAN IP. I think this also applies if the link is a wireless uplink. So not required.