It's definitely more efficient to focus on one genre or one domain at a time. But of course you need to take enjoyment into account. If you stick to one domain for too long then it can become really tedious.
In the guide I said that in the beginning I recommend immersing in slice of life movies and TV shows. In slice of life shows you've got a limited range of vocabulary, and the words that are being used are common across the entire language. This is the recommended first domain. Having a solid foundation in the initial domain makes it much easier to learn new domains. When you know the most basic vocabulary, you can move forward really quickly. You build up a strong base in one domain, increase your overall comprehension, and then use that to your advantage as you move on to new domains.
If you focus your attention on a specific domain of your target language, it will be much easier for your brain to absorb the patterns. By narrowing your field of study and taking it one domain at a time, you can ensure that your brain can fully focus on one thing and master it before moving on to another. This approach is much more efficient than trying to learn many things at once.
Every time you choose a new genre, move to a different domain, it will have a different set of commonly used words and expressions. Domains can be similar to each other or very different from each other. Some specialized domains can be quite difficult to understand without lots of study. Try not to jump to a new domain that is too distinct from other domains you have immersed in. Also, try to get a solid foothold in the domain before moving to the next domain.
Once you reach advanced stages, worrying too much about differences between domains is not going to be productive. For example, if in the beginning you're immersing only in slice of life TV shows, in later stages you don't have to distinguish between anime and reality shows, or anime and dramas. Moving from one domain to another becomes pretty easy.
If you immerse in only one genre, you're going to quickly increase your understanding of the content in that genre. Once you understand a certain genre well, your overall progress in the language will slow down until you tackle a new domain. So, sticking to one genre for too long is also a bad idea, but jumping between many genres will result in facing too many unknown words if you're not fluent yet. Ultimately it's about finding the balance between trying to master domains of the language in the most efficient way and immersing in what looks interesting. Prioritize enjoyment over "efficiency". The fun cut to Japanese is almost always the shortcut.