All of what you read below applies to Battlefield 6, as tested in Labs and the Open Beta, including my own personal settings, summarized at the bottom of this sheet.
This is the new version of my old guide for BF4 through BF2042, for Battlefield 6. BF6 uses a revised mouse input system with a lower base sensitivity and a higher max sensitivity, and by quite a lot too. Editable both in-game with decimal points via arrow keys, and in config files, with input that isn't just emulated controller input like 2042, it's a paradise by comparison.
If you wish to more finely tune your sensitivity, keep reading.