With so many actors it could be very steep. Like 51% capacity has 99% chance of success and 49% has 1% of success and 40% has practically zero chance (these are made up numbers).
It could also be quite shallow as in 1% capacity gives you 1% of success... that would actually be quite bad and invite malicious actors to test the system with regular attacks.
It's a race of who can get to N blocks first. The higher N the "steeper" it is. N is set by the merchant so as to balance security with quick transactions
I haven't had nearly that much trouble with more recent videos, which seem to have excellent sound reproduction. It very much depends on the original upload quality though. Some older videos (anything stuck on 240p or lower) are from a time before HD uploads were a thing, and surely used more aggressive compression.
Some uploaders are also simply unskilled; I'm mostly after video game soundtracks to listen to in my car, and especially for newer soundtracks you have to watch out for the uploaders trying to be "first" to gain the popularity, while sometimes using poor settings or a bad rip. There's nothing youtube can do to improve bad source audio.
they seem to use Opus with 160 kbit bitrate now, you can view the formats with youtube-dl -F. Bandcamp disallows using compressed source audio, i wish youtube would too.
