SharePoint Framework natively support building Client-Side Web Parts using React. Here is a sample Web Part illustrating the different pieces of a Client-Side Web Part built using React.
So you would want to build a SharePoint Framework solution with a couple of Web Parts. But then you wonder: how would SharePoint know which Web Part it should run when? With no explicit relationship between the code and the manifest, would you need a separate project for each Web Part instead?
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