Packets per Xfer - This is self explanatory, it sets the number of packets that you want to send or read per each transfer using the streamer application.
Xfers to Queue - This one sets the number of transfers that you want to keep in the pipe line using streamer application. When these two parameters are set to high number then you can see better throughput numbers.
CY_FX_EP_BURST_LENGTH is basically deciding the burst size of that BULK endpoint. This is the feature that is there with Superspeed BULK endpoints. Refer to section 188.8.131.52 to get more details regarding this.