AFAIK Remote Config is just a server side key value store with customisable values based on audiences (e.g. random 50% for A/B testing, all people from Country X). This means all behaviour changes will require code to be deployed in the first place.
Also, from Firebase Docs[1] "Don't attempt to circumvent the requirements of your app's target platform using Remote Config."
"Firebase Remote Config allows you to change the look-and-feel of your app, gradually roll out features, run A/B tests, and deliver customized content to certain users, all from the cloud without needing to publish a new version of your app."
With hot code pushing, you're deploying newly written code/functionality, post release (opening possibility of up MiTM attacks etc).
With Remote Config you deploy the code, then decide what to show to users post release. This gives Apple a chance to review all the code submitted to the App Store.
In the case of rolling out features an A/B tests, you'd make a release including a feature, but only enable it x% of your users using RC. You can then obviously enable it for everyone if it passes your A/B test or if you're happy its working.
