After thinking a lot, this is what I know.
DAC Authentication is controller-based, and as I used local database for authentication check, changing it to RADIUS will still require that webpage to be present.
In order to switch to WPA2-Enterprise, I need to configure each and every access point to use WPA2-Enterprise, and point them to the RADIUS server. That's mainly because I use Fat APs, if the access points I have in my environment are thin APs, they can simply fetch configuration from my controller.