Rankings are going to vary per channel anyway. The only way to "find" a ranking keyword is to use the keyword explorer, think of some more targeted keywords that other's aren't using, and see how they score out of the gate. But it's also how your video performs overall that will probably determin how the keyword actually ranks. You do this by looking at your video keywords AFTER the video is public, and with your setting set to incognito mode so you're not getting biased results, and then you'll see if you rank number 1, or number 10 etc.
I would say though, it doesn't necessarily matter if you rank number 1 or number 5, as long as you show up at all on the search results. If you show up, your thumbnail and title will then determine if the video actually gets clicked. Ranking keywords give you the OPPORTUNITY for a click. If your thumbnail is messy and unattractive, someone else's thumbnail that looks more professional might end up getting the click.
If few videos use a specific targeted keyword, you'll rank. But once other videos enter the playing field, you'll have more competition. And if another video has a better thumbnail and title, and is watched more, they will start outranking you. So rankings are pretty fluid.
So you want to TRY and get some great keywords, but you also want to make sure yout video it'self, and it's thumbnail are amazing as well, otherwise your keyword ranking may change over time.