Yes its true that you wont be able to create contentTypes after you used yarn build and yarn start, but thats the point.
if you develop (creating content types etc is developing) on your Prod environment , you can accidentally delete stuff etc, if you misclick.
I would recomment you develop the content types locally, then build a docker image where you run yarn build inside the Dockerfile and use yarn start as an entrypoint (or something along the lines)
then deploy that image to prod. Also make sure to make regular backup of your production Database.
For development that docker-compose file with mounted folders should suffice.
But for production read up a bit (idk if its in the docs , but i guess you’ll find some guidelines somewhere)
Good luck 