I haven't seen any good yt keyword research guides recently so can't help you there. Would take me too long to write up anything better then what you can find with a Google search so no point.
In terms of SEO, here's a very basic overview: when you first upload a video, YouTube knows what keywords to rank it for with the metadata you provide including title, description, tags, etc. as well as what it can detect from your video itself which it analyses during the upload. The position that you reach for each keyword will depend on many factors including but not limited to metrics and channel authority.
As your video gains impressions, YouTube is collecting data on user behavior, processing that data through their search ranking algorithm and adjusting your videos ranking accordingly. This data is of course compared against your competitors videos who are ranking for the same keyword/s.
In an oversimplified way, what that means is, if your competitor is getting a 5% click through rate from search traffic for 'keyword', and your video is getting a 1% click through rate; that is a signal to YouTube's search ranking algorithm that your video isn't as relevant to that audience which means you may not be able to outrank the competitor. It's not that cut and dry of course but you get the point.
CTR is just one of potentially thousands of data points that YouTube is using to calculate your ranking.
In summary, here's a basic YouTube SEO strategy to get you started; you'll want to do something like this to have a high success rate. Optimize metadata for keyword relevance as per current best practices, optimize title/thumbnail/etc. for click through rate, upload a video that will yield better organic user behavior signals with your audience then your competitors videos that you are trying to outrank, boost important metrics after uploading to increase initial organic traffic exposure (views, watch time, likes, click through rate, etc.).
Remember, if your video doesn't perform well organically with your audience then you won't maintain a high search ranking.
With keyword research, you'll want to identify terms that have a level of competition that you can actually rank for. Over time you will figure out what competition you're capable of outranking and you'll get better at finding them quicker. Don't get too caught up on finding the perfect keywords, just get started. Start with lower comp stuff and see how you go. It's also worth noting that not all channels can rank (warm up channel, get some watch time if vids don't show up at all; older channels may work better).
Good luck!
