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.
Looking for sub niches and niches within a niche have been a good way for me to find tags where my smaller channel can actually compete.
Example for gaming:
1. Main niche gaming.
2. A sub niche of gaming - Strategy games.
3. A sub niche of Strategy games - Grand Strategy games.
4. A popular sub niche of Grand Strategy games - CK3.
5. A less popular sub niche of Grand Strategy games - Imperator: Rome.
6. A popular sub niche of Imperator: Rome - Let's plays.
7. A less popular sub niche of Imperator: Rome - tutorials.
The larger your channel is the higher up in the sub niche three you can compete for. As a smaller gaming channel you probably need to go pretty deep into the sub niches to find a less crowded spot where your channel can actually compete for the key words.
A new channel could perhaps compete for a less popular game (5) and a less popular niche for that game (7). So you might start doing tutorials for Imperator: Rome. As the channel grows it can start find an audience for the let's plays (6) so you start doing let's plays for Imperator: Rome. As the channel grows even more it could start compete for more popular and competitive games inside the same overall niche (grand strategy games 3) so you start doing videos for CK3 (4) but as with Imperator:Rome you probably start with a smaller less competitive sub niche for CK3.
And as your channel starts growing even further you might leave the grand strategy niche and branch out to it's parent niche and start doing videos for different strategy games (2).
This i basically a good way to think about it and to find keywords where you can actually compete. In most cases you need to find a keyword where the competition is just below your own channels level and the smaller the channel the smaller the niche you need to find.
To some people it may feel strange to target really small stuff that fewer people search for but remember it's most likely far better to be the number 1 result for something only 10 people search for each day than to be number 200 for things 1 million people search for each day. Then of course sometimes you get lucky and find something that a lot of people search for and with very little competition.