So... I "yolo'ed" it a little bit, in a nutshell this is what I did:
Copied the current /etc/hostpad.conf to /etc/hostpadAC.conf
Shutdown the machine
Disconnected the current AC dongle and connected the N one in the other usb port
remade the hostpad.conf using armbian-config
edited /etc/default/hostpad to include both config files like this ---> DAEMON_CONF="/etc/hostapd.conf /etc/hostapdAC.conf"
edited /etc/init.d/hostpad to include both config files like this ---> DAEMON_CONF="/etc/hostapd.conf /etc/hostapdAC.conf"
Both access points are here but only the N one works, the AC one gets stuck at "gathering ip address" on my smartphone.
What this noob (me) did wrong? What is missing?