This document provides information on distance measurements depending of the Bluetooth LE data rate (1Mbps, 2Mbps, LR S=2 & LR S=8).
The FRDM-KW38 boards are used to perform the measurements.
Results are similar on KW37 and KW39.
Tests video released here:
https://www.nxp.com/video/kw39-38-37-bluetooth-low-energy-long-range-field-tests:KW38-MEASUREMENT