UPDATE 5-19: Just spotted the improvements to First Release in my tenant
When first release was announced about a year ago it was a minimum viable product. You had two options: enable it or disable it. If you have two tenants – one with first release enabled(acceptance) and one with first release disabled(production) – you could run into a problem where you get some new features on your production tenant first.
This problem is now tackled by Microsoft. During Ignite Microsoft announced they are enhancing first release. Soon you will be able to choose which users will get First Release.