There is not a best practice document for the specific creation of a dev environment but you can follow the regular installation instructions included in the product downloads and make some adjustments based on your needs.

I would suggest putting a development workflow, quickfields, forms, sdk, and the laserfiche server all on it's own server (virtual or otherwise).

You will also need a SQL Server which you can add into your enterprises existing architecture or create a local instance on the development machine. 

Additionally I would suggest using a service account dedicated for development.

Without setting up this environment you can control development risk by adding another repository as you mentioned but this will only protect documents at a limited level. You will continue to have risk in Workflow, Quickfields, Forms, and SQL as each of these can potentially "runaway" and impact the production environment. 

With Rio Licensing, you will have to purchase a separate license for QuickFields, so talk to your sales rep for pricing information. Let them know it's for development use. You can opt to use the same production instance of QuickFields and be vigilante as you do run the risk of creating a runaway session and preventing other quickfields sessions from performing.

Ultimately all of this rests on the mighty backbone of your SQL server, so having a dedicated development area there is vital.

Cheers,

Carl