Board Thread:Theories and Speculation/@comment-33256714-20171005000302/@comment-6769189-20171005110736

Its never specified to what extent or how efficient it is in either of those fields. Even Gaara was able to track Lee. Kakashi pulled out the Sharingan to look at Lees chakra. It's not unreasonable that Neji was doing the same thing since no one in the chapter mentioned him needing the Byakugan to see Lee's movement. Matter of fact those abilities I don't think were ever attributed to the Byakugan.

The Byakugans wide field of vision and ability to focus on any/all points in that FOV would help