What is the difference between e.g. FLAPFC10E and FLAPFC11E devices?

The digits in the part number specify the hardware version of the device.

PowerFLARM Core devices with the digits 10 imply hardware version 1.0 and do not have the option for audio out. Digits 11 imply hardware version 1.1 and have the option for audio out.

PowerFLARM Portable devices currently have digits 23 and 24. Hardware version 2.4 is an updated version with improved out-of-band filtering.

The character 'C' in e.g. FLAPFC11E (PowerFLARM Core) or 'P' in e.g. FLAPFP24E (PowerFLARM Portable) indicates that the device has a 1090 MHz receiver (SSR and ADS-B).

The last character (e.g. 'E' in FLAPFC11E) indicates the radio band version of the device. More information is available here.