Both Angular and React are not server-side technologies in the first place. You can have server-side aspects, that's true. Both of them work fine in the combination of HTL/Sling models on the server-side plus the respective JS framework in the browser.
Running React code within AEM is possible, but at the moment there is no product support for it (you need to build it on your own).
Any idea if we have to compare Angular+AEM vs Angular+React, which one is the best option to go with?
Please point me if you have some POC having some components in any combination.