Hi anonymous user,
Glad to see your interest in using Static Web Apps.
The app works but, is a correct architectural approach or is better only publish our app to an AppService?
IMHO, this is fine because your React app is doing your rendering client side.
There are any security/cost related/whatever topic that makes StaticWebSite + AppService approach better than only AppService deploy?
I can't provide any insights on costs due to the nature that Static Web Apps is still in Preview while the product team assess how best to meet the needs to users with this offering. Static Web Site is underpinned by Azure Functions, so to your point, the biggest advantage I would say is geographical distribution and scalability along with key features listed.
Another option to consider is that fact you can host your API as an Azure Function and easily integrate with your static web app; see https://video2.skills-academy.com/en-us/azure/static-web-apps/apis.
Configuring CNAME between App Service, Static Web Apps, and Azure Storage hosting are similar, so I wouldn't consider that a determining factor.
Regards,
Ryan