What is the use of PNP in SPFx?
You may choose to use the @pnp/sp library when building your SharePoint Framework (SPFx) web parts. This library provides a fluent API to make building your REST queries intuitive and supports batching and caching.
Can I use React in SharePoint?
The primary Fluent UI React package, @fluentui/react, simply exports components from the office-ui-fabric-react package used in SharePoint Framework projects. At this time, you should continue to use the office-ui-fabric-react package in your SharePoint Framework projects.