If you are using cv::VideoCapture then this will not have any impact. The module you are refering to (cv::cudacodec::VideoReader) is part of the contrib repo and has “nothing” (it uses it to demux the video) to do with cv::VideoCapture from the main repo.
Regarding cv::cudacodec::VideoReader if you want maximum performace you should increase the number of decode surfaces in use. This will have the side effect that the sleep is unlikely to be called because there will always be a surface available unless you are consuming the decoded frames too slowly.
Just out of interest why do you need such a high frame rate?