Do I need a Framework for Deploying a Postgres + Express + React + Node App

I am a new self-taught developer.

I have created a simple full stack app (learning management system) using PERN stack. Now, I want to deploy it to learn the end-to-end process of creating a web app. I have a plan to make incremental improvements in the app and add more functionality to make it usable.

While researching for deployment, I came across various posts that doesn’t recommend using create-react-app for production ready React apps. Further, this official article from React recommends using some toolchains for deployment (I think it is another name for Frameworks or set of tools):

Another alternative is to optimize the code using Webpack etc. before deploying it. I am neither familiar with any React Framework nor much aware of performance optimization for PERN apps.

If I have to use a framework, then my existing code may not work. I may have to do complete review of the same to make it suitable for the framework.

What is the best way to deploy my PERN app which I can scale in the future. (I have partially understood the concept of client side and server side rendering. As of now, users have to login to use app. But in the future it will be like the users can see the page (to take advantage of SEO) but need to login in order to interact with the site).

Do I need to learn a framework? (In that case I may have to develop all the code in that framework to maintain compatibility). If this is the case, then I will be glad to know which one?

Or, is there other way to deploy fully-functional PERN apps ready to use by potential customers.

Eagerly looking for some answers as I am completely confused at this point.