whats the time difference between the two before features hit first release then standard.
I don't believe there's a strict timeline; that said, Microsoft has been very good about announcing what's hitting first-release and standard release in their Tech Community forums. Try exploring those; I primarily use the SharePoint forum, found here.
This is the default option where you and your users receive the latest updates when they're released broadly to all Office 365 customers. This gives you extra time to prepare your support staff and users for upcoming changes.
With this option, you and your users can be the first to see the latest updates and help shape the product by providing early feedback. You can choose to have individuals or the entire organization receive updates early.
Time between a feature being released in first release and it being released in standard release varies by feature. As stated in the first link:
Once it is determined that the feature is ready for broader release, it's applied to everyone else, including people who have selected Standard Release.