Using youtube-dl: Does adaptive bitrate (ABR) affect image quality?
Adaptive streaming is accomplished by switching between pre-encoded streams of different bitrates and/or resolutions. But the bitrate within any given pre-encoded stream does not vary too much.

YT-DL, with your command, will select the 'best' video stream, usually the one with the highest bitrate and resolution, and return its URL. This URL is a direct resource address, and there will be no switching when downloading it, even if your network gets congested.