I do not believe there is a specific version you need to use. Revit 2019 comes with Dynamo version 1.3.3 or 1.3.4. There should not be an issue with using Dynamo version 2. You can download a version from the Dynamobim website..
Which version better to use will depend on your situation. Things like, what are others (in your company) using., do you already have scripts for the 1 version (they might break in the 2 version) and so on might define which version to use.
(Version 2 had a big overhaul of many nodes)
Louis

Please mention Revit version, especially when uploading Revit files.