Extra 1 is 2min 18sec and Extra 2 is 7min 59sec.
Honestly, there are fan made music videos on YouTube that are more fulfilling, but if you loved the series it's easy to watch these 10 minutes. It doesn't add much, but the show was a 10/10 for me so I'm giving this an 8/10.

Extra 1 is a voice over by QingCang giving a very generalized recap of the 300 years he and Orchid have been together so far. The lines are new but all of the scenes shown are clips taken from the original series. It's simplistic but still sweet.

Extra 2 is like two music videos. A montage of clips and dialogue from the series play during the first song.
During the second song, that continues and then it shows two things that weren't in Ep 36 (though they didn't have that much of an impact for me):

1) Shows Orchid writing something and sending it into the sky while a few lines of Chinese script play onscreen. Unfortunately, iQIYI didn't add translations for the text so I have no idea what it said. Does anyone else know?

2) Shows the bone moon re-materialize into QingCang, which wasn't shown in Ep36, but his line "I'm back" is left out, and he kisses her on the forehead instead of the lips (which is a visually pretty end tableau but not as satisfying as the original end).