I recently replaced my old Samsung NVME with a 990 PRO 2TB, I tested its speed with Magician and CrystalDiskMark and they both gave me a speed of 7450MB/s. I turned Bitlocker ON and the speed on Magician went down to 3487MB/s but remeined the same on CrystalDiskMark. Apparently Bitlocker has a big impact on speed.

My secondary Samsung 970 EVO 2TB is not affected by Bitlocker, the speed remains the same.

Are you having the same issue?