Heya! First time poster 
We’re currently trying to configure an Audience RBD25G-5HPacQD2HPnD (1x2.4GHz and 2x5GHz interfaces) to use its second 5GHz interface, which is usually intended for meshing multiple Audience MikroTiks together, as a stronger 5GHz WiFi for modern devices to get longer reach out of it.
Our idea is: One SSID, use 2.4GHz for very old devices (legacy WiFi basically), use the first 5GHz interface for more modern devices which only support a/n and use the second 5GHz interface for all other modern devices in ac only mode. The idea being that devices only supporting a/n won’t slow down devices supporting ac this way.
Is this even feasible? So far iPhones connecting to it will try 2.4GHz first, then get pushed shortly to the 5GHz ac standard, however revert back to just the a/n one after a few seconds for some reason and then finally stay there all the time. Since modern iPhones support ac it should theoretically stay at the 5GHz ac card, not the a/n one.
Thanks already for your answers!