I want to have a 2.4Ghz and 5Ghz network with the same password, and assign clients an IP from a DHCP server running on 10.20.20.1. Using the WispAP quickset I managed to setup the 5Ghz network, with the hAP ac^3 receiving an IP of 10.20.20.107 and the connected clients being assigned their IPs correctly, but cannot setup the 2.4Ghz one. Attempting to use the dual home AP quickset results in both WiFi networks becoming impossible to connect to, even when the hAP is running its own DHCP server, NAT, and subnet. Is this a limitation of my hAP ac^3? I doubt it is because every other Mikrotik device I have used is awesome! This must be user error.

In the interface list when connecting via WinBox, wlan2 (5Ghz) is RS and wlan1 (2.4Ghz) is just slaved.

Any help would be greatly appreciated

Looks like a quickset problem.
When changing to dual AP, did you start again from default config ?
Quickset is typically only to be used ONCE after default config, then never again (until starting again from def config).