Deploying a Web App is easy.
Deploying a Web App is nothing more that making a static version available for a certain URL.
There have been issues deploying a Web App using the new code editor.
People have reported that subsequent deployments using the new code editor will change the link to the Web App.
I'm not certain what the exact status of this is at the moment, but you might want to do some tests before
telling everyone what the link to the Web App is.
You need to consider how many simultaneous users the Web App will have.
See:
What people usually focus on is the 30 Simultaneous executions limit.
If the Web App will have usage that is evenly spread out over the day, then you might be okay.
But if all or most of the 500 users are going to be mostly using it within a 1 hour time span or less, it's probably not going to work for you.
If you find that the 30 Simultaneous executions limit is a problem, then obviously you'll need to use something else.
You can host a site with Firebase Hosting.
If you can't use the Web App and need to host the site somewhere, then you'd probably need to use Google API's for any services
that your Web App is using. For example if your Web App does something with Google Sheets, then you'd need to use the Google Sheets API
instead of the built-in SpreadsheetApp service.
If you wanted to publish the Web App to the Workspace Marketplace, that's different then deploying.
Getting verified and approved from Google is more difficult, but you may not want to have the Web App listed in the Marketplace.
You can get the Apps Script project verified in order to avoid the message that it's not approved by Google,
and still choose to not list it in the Marketplace.
If the Web App runs as the user, and the user must be signed into a Google account, and the user is signed into multiple
Google accounts then you'll get lots of errors because of a bug.