Regarding the capability:
FX2LP cannot add UVC headers but if you use FPGA then 640X480 at 30 FPS can be handled. But if you are implementing UVC+UAC FX3 would be a better option.
Currently we do not have any example project where UVC+UAC is implemented in FX3, but this is the best option(in terms of capability) for implementing your application.. But here are few options if you are using FX3:
1. You can use I2S block for transmitting Audio and GPIF for video and receiving audio OR
2. You can use I2S block for transmitting Audio, SPI for receiving audio and GPIF for video streaming.