:lol:
It's a "matter of style" - in other words, depends on the tastes of the author/reader/compositor etc.
The traditional "English UK" style for Title Case is option A. Like 38th, I prefer that.
However, I'm not sure it matters too much?
My understanding is that, songtitles aren't copyright-able anyway, so the case probably doesn't matter when registering.
Also, bear in mind that the case of songtitles would probably get standardised in a list of songs - eg on a CD case. So, even if you think "King of Speed" is what you decided to call it, you might find that someone calls it "king of speed" on their CD case when they cover it, because their style guidelines for their artwork dictate "no capitals".
Interestingly, although I prefer option A for titles (I am "English UK" after all :lol:), I personally use option B.
This is because all authoring tools I use or have experience of cannot automatically apply the strange and varying "English UK" rules for Title Case. So to produce standardised titles in documents, I follow the tools' standards - in a title, all words start with a capital.
This approach has spilled over into my own song-lyric documents.