My personal opinion is build it from scratch. Dev/Test environments are made to be just that. I have done both and have seen some pretty catastrophic issues with cloning, even with them on separate networks it’s just a dirty way to do it imo.
For Testing I build one reasonable beefy VM, nothing crazy but enough to unpack compressed files quickly and load tables into memory on deploy. My ideal VM sits on an SSD, 32gb RAM (not super necessary and mileage varies based on DB size), i7 or decent Xeon with at least 4 cores allocated to it. Windows Server 2016 (you can get a 180 day trial if you don’t have licensing), SQL 2016 also (you can get the full thing for free in Dev environments). Create your base VM,install Windows + Roles and features (IIS, file services, etc.) and SQL, followed by reporting services, then take a back up. From there mimic your lives environment from a drives and directories standpoint and then install the latest RL (found on epicweb). Open the admin tool, connect your Database server, Add new DB, Create new App server, add a company, add your license (can be the one from Prod), verify you can login, then update to the latest UD. Install and create a task agent make sure that starts (might need to give your user impersonation rights). Next thing you can do is take a backup of your prod DB and restore it to that DB you created before, depending on how closely you modeled your app servers to your prod environment I would recommend creating a new app server to connect to your restored prod DB. Verify Login, update as necessary and your off to the races, don’t forget to clean up and kill prod Agent tasks such that people aren’t getting erroneous emails and files aren’t being accidentally overwritten. The more you do from the beginning the better you will understand it in the end, and the better off you are from a troubleshooting standpoint.
Side note the performance and diagnostic tool is your friend, it has a config checker that will help tweak you identify areas that need to be fixed or adjusted after you complete the install.
Edit: As far as documentation is concerned: