Hey there @Xepobopa! I apologize for the delayed response on this one.
You should be able to get away with a Single Page Application (SPA) for your React frontend while registering your Nest.JS Backend/API - I definitely recommend checking out our Architecture Scenarios documentation for high level overview.
I also recommend checking out our React sample app as well as the following blog which outlines adding authorization to a Nest.JS API:
Hope this helps to clarify!