Storing assets within the AWS ecosystem

I am newbie to AWS development (but have extensive experience on traditional development).

I need to build a web app with ReactJS frontend, NodeJs/Express backend, MySQL. Its SaaS app possibly with thousands of clients. There will be a use case where we have a Parent client having hundreds of Child clients.

So, parent-child relationship within clients itself. Child's settings supersede parents. Each client (doesn't matter child or parent) will have its unique logo and style. Child may or may not override logos and styles. If Child doesn't override it gets from Parent Client. and so on..

I can handle logos/styles/settings at the time of client's onboarding using some configuration tool. Thus, I will upload/change the logos/styles/settings for parent and/or child clients- at the time of client's implementation. I need ability to change these logos/styles/settings, later, whenever clients demand so.

What are my options on how to design the app: (again, I am newbie to AWS)?

1. Storage-wise, what's the best place to store logos/styles/settings? If AWS S3, will it provide me certain folder layout to handle parent-child or should I dump all images/styles(css) in single folder with client's prefix on each item?
2. Other option, pulling of images/styles/settings during runtime when site renders. Thus, I will to determine parent-child relationships for every click on web app and determine where to grab the resources from. Little overhead at runtime since I am pushing the parent-child logic at runtime instead of configuration-time/one-time.

Any thoughts/alternate design/suggestions/pros&cons with respect to AWS environment?