nRF52840 USB CDC ACM baud rate question

Hi. We are using the USB CDC example to send data to a windows PC over virtual comport.

First question is that in the sdk_config.h file NRFX_UART_DEFAULT_CONFIG_BAUDRATE = 30924800 which is 115200bps. However we are transmitting about 64,000 bytes in about 2 seconds which is 256,000bps ? Sometimes it is even quicker than that.

Second question is, that on a slower windows computer sometimes a few bytes are lost when reading the data in. We would like to adjust the baud rate (lower), but seems from above question that it can't be adjusted?

Where is the baud rate set for the USB CDC example, or is it no and its all 'virtual'?

I checked all the baudrate settings in sdk_config, and they are all 115,200bps.