2.4 GHz Wifi - BT On - D: 63 U: 71 Mbps
2.4 GHz Wifi - BT Off - D: 66 U: 78 Mbps
5.0 GHz Wifi - BT On - D: 376 U: 390 Mbps
5.0 GHz Wifi - BT Off - D: 366 U: 376 Mbps
So, values are almost the same with BT ON or OFF (at least, on my Mi 6 and Huawei W1 watch )