To work with RealFlight, your controller needs to present itself to Windows as a USB game controller (or joystick). I'm pretty sure the Boxer can handle that. When you connect the Boxer to the computer via USB, you would choose to do so as USB Joystick rather than USB File Transfer. If you prefer to go wireless, you could use a USB wireless receiver but you'll be limited to 8 channels.
You would set up the TX with a model that's a simple 4-channel airplane, plus assign all switches to radio channels. Via USB, you can use as many channels through the joystick mode as the TX allows in general. If you go wireless, set up channels 5-8 on switches.
Then in RealFlight, you would use the Controller Profile to edit the way channels on the TX are assigned to the channels in RF. The models in RF are all tied to "standard" channels within RF. After you spend the time setting up the Controller Profile, all of the models will work. You don't need to set things model by model.
If you're on a pretty current version of EdgeTX, use "Classic Mode" for the USB Joystick. It's more trouble than it's worth (and not necessary) to use the new advanced setup where you try to map things on the TX to specific Windows game inputs. You can sort all that out using the Controller Profile in RF.
