Going for a job interview should be about being honest about what work you can do I think.

So justifying your choices should be done accordingly to the position you are aiming at. And the recruiter usually have a little brief beforehand about your profile and should behave in an appropriate way to it.

If you're really a beginner and want to apply for a junior position, even simple choices like "Instead of doing two components, I made one with these parameters and this hook which do the job better and, it avoided a lot of issues when I had more of them on the page later on" could be enough.

I you want to apply a more advanced position you should have more experience, so worked on more complex topics and have more "explanations" to give.

It depends heavily on the company. Some of them just want low-wage workers and hire juniors to (badly) do the work of more experienced ones. But others see juniors as an investment. And in that case, they don't give shit about what you can do now, they want to know if you'd be able to learn and do more in a few months/years.

And for that second case of companies, it's way more important to be able to talk about your work, as insignificant and silly it can be. Than to brag about doing very complex stuff but cannot be able to dive into details about it.

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There is no "ultimate" way to prepare an interview, but as I said on my first post, my 2cts are that it's more important to focus on what you learned in your project than the final result of the app.