You're probably using a wireless USB receiver such as the WS2000 to connect. If so, the receiver is limited to 8 channels. You'll only be able to use Gear, Aux1, Aux2, and Aux3 for switches/buttons with RF.
You don't need to try to match your channel numbers on the iX14 with the numbers in RealFlight. Use the Controller Profile to map those four channels in the iX14 to the most useful channels in RF.
A typical setup would be Switch A on Gear for landing gear, Switch D on Aux1 for flaps, Switch B on Aux2 for Flight Modes, and then the button (Switch I) on Aux3 for panic or thrust reverse (function depends on the model). Then in the Controller Profile you'd map Switch A to RF Channel 7 Smoke, Switch D to RF Channel 6 Flaps, Switch B to RF Channel 8 Mode, and finally Switch I to RF Channel 12.
That will work great for planes in RF, but if you plan to fly helis then you'll have to change one of those four things such that you assign a switch to RF Channel 9 for heli Throttle Hold. All helis in RF use the Throttle Hold feature.