> that I study existing well designed codebases.
Proceed with extreme caution. This is highly subjective and often results in a blind leading the blind scenario. For example how do you determine which code bases are well designed if you yourself are not comfortable determining such?
Instead, heed the guidance of some of the other comments and just start building things. Plan on failing and solving for the failure. That’s called practice. With enough practice you will know what works well for you. If you are measuring things along the way you will also know what’s slow.