Under wireless networks, set the following advanced features for better iOS compatibility and throughput and to force clients to connect to a closer AP when roaming:

Enable multicast enhancement (IGMPv3)
DTIM 2G Period = 3
DTIM 5G Period = 3
2G Data Rate Control Minimum = 18Mpbs
Also require clients to use rates at or above the specified value
5G Data Rate Control Minimum = 18Mbps
Also require clients to use rates at or above the specified value

• On each AP make sure “config → radios → allow meshing from other access points” is checked
• Make sure on the controller that “enable connectivity monitor and wireless uplink” is checked
• Adopt all APs that you're going to use via a wired connection (those that will be used wired as those that will be used via wireless uplink)
• For the APs that will remain hardwired be sure that “config → wireless uplink → allow meshing to another access point” is unchecked.
• For the APs that will be wirelessly linked be sure that “config → wireless uplink → allow meshing to another access point” is checked.
• After everything is saved, power off your wireless APs that will be “islands” or not hardwired, then plug them in without connecting the LAN port of the PoE. It should go to isolated then “connected (wireless)”.
• Note, if you want to connect a PC or printer, etc directly to the LAN port of the PoE so that the AP acts as a wireless bridge, you will need a switch in between the AP and the PC, printer, etc.