Youtube offers various codecs, also including VP8 at all resolution/framerate settings H.264 is offered on (not all formats will always be available). For example, here's the youtube-dl format list for a well-known video:

  [youtube] dQw4w9WgXcQ: Downloading webpage
  [info] Available formats for dQw4w9WgXcQ:
  format code  extension  resolution note
  249          webm       audio only tiny   49k , opus @ 50k (48000Hz), 1.18MiB
  250          webm       audio only tiny   65k , opus @ 70k (48000Hz), 1.55MiB
  140          m4a        audio only tiny  130k , m4a_dash container, mp4a.40.2@128k (44100Hz), 3.27MiB
  251          webm       audio only tiny  136k , opus @160k (48000Hz), 3.28MiB
  394          mp4        256x144    144p   73k , av01.0.00M.08, 25fps, video only, 1.72MiB
  278          webm       256x144    144p   97k , webm container, vp9, 25fps, video only, 2.25MiB
  160          mp4        256x144    144p  107k , avc1.4d400c, 25fps, video only, 2.05MiB
  395          mp4        426x240    240p  159k , av01.0.00M.08, 25fps, video only, 3.42MiB
  242          webm       426x240    240p  217k , vp9, 25fps, video only, 4.04MiB
  133          mp4        426x240    240p  290k , avc1.4d4015, 25fps, video only, 4.48MiB
  396          mp4        640x360    360p  340k , av01.0.01M.08, 25fps, video only, 6.68MiB
  243          webm       640x360    360p  396k , vp9, 25fps, video only, 6.96MiB
  134          mp4        640x360    360p  484k , avc1.4d401e, 25fps, video only, 8.27MiB
  244          webm       854x480    480p  586k , vp9, 25fps, video only, 10.03MiB
  397          mp4        854x480    480p  603k , av01.0.04M.08, 25fps, video only, 11.37MiB
  135          mp4        854x480    480p  741k , avc1.4d401e, 25fps, video only, 11.56MiB
  247          webm       1280x720   720p 1035k , vp9, 25fps, video only, 17.67MiB
  136          mp4        1280x720   720p 1077k , avc1.4d401f, 25fps, video only, 16.72MiB
  398          mp4        1280x720   720p 1133k , av01.0.05M.08, 25fps, video only, 22.07MiB
  399          mp4        1920x1080  1080p 2106k , av01.0.08M.08, 25fps, video only, 40.74MiB
  248          webm       1920x1080  1080p 2666k , vp9, 25fps, video only, 58.46MiB
  137          mp4        1920x1080  1080p 4640k , avc1.640028, 25fps, video only, 78.96MiB
  18           mp4        640x360    360p  601k , avc1.42001E, 25fps, mp4a.40.2@ 96k (44100Hz), 15.19MiB (best)