I assume you've already decided you're aiming for a company using these sorts of problems, you have a limited amount of time to practice, and you want to make the most of it. A no-nonsense, practical answer: single best thing you can do is get Leetcode premium subscription.
This solves three problems for you:
- You have access to reasonably well curated answers, often with alternative solutions, right next to the problems you solve. This saves you time on doing your own research and is definitely more efficient than watching videos. Go back to those for problems you can't wrap your head around and really need to put some extra effort into,
- You have access to Top 100 questions lists for different companies. Following those is a good way to keep yourself looking at high frequency, common questions, so you'll be covering useful material rather than going deep into some off-tangent topic,
- You have access to mock interview sets, which will choose problems to solve for you. That's important since you will inevitably develop some sort of bias in what problems you look at, either picking things you know how to solve, or picking things you're most concerned about and neglecting other kinds of problems.
After that it's just about putting in the time and effort to practice. Don't wait with mock interviews too long as they tend to uncover blind spots quite effectively. Furthermore, try to write down the complete solution, don't depend on write-compile-fix cycle too much - many companies use whiteboards or scratchpads that don't come with a compiler, and you'll need to be comfortable in solving these problems without that support.