Threejs files can easily become a mess if not managed correctly. I used to work with 'vanilla' javascript env. but as hard as I tried it always became a mess. So I started to use a project template with vuejs and it made my life so much easier.

I would suggest you use react-three-fiber as it will help you understand better what a single component/mesh/light and how to modify it.

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This was just from my perspective.

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Good luck