Hi, on my blog there are many test on youtube bitrate and quality.
Upload your video in 1440p and NOT in 720p or 1080p... 2K resolution boost bitrate x3 in youtube transcoding process! Youtube Best Settings Guide: Uprez your video to 1440p take advantage of the higher bit rate boost
My youtube video download test (h264 and Vp9): Test video quality 720p 1080p 1440p 2160p max bitrate which compresses youtube For other resolution: Best Youtube export settings for 720p 1080p 1440p 2160p
for 4K 25mbits is ideal... for 2K 20mbits... best h264 encoder is MEGUI: high quality h264 file... for vp9 media encoder with webm premiere plugin