Hi Grant,
The Solution Deployment Tool will create a copy of this layer in whichever ArcGIS Online organization/ArcGIS Portal that ArcGIS Pro is currently connected to. There is no need to download a feature class version of the layer - The Solution Deployment Tool will also allow you to load in your data and update fields and domains (although this should be done with care as too many schema changes can have dependencies in the applications that use this layer).
If you find that you absolutely need a feature class copy of the layer, you can use the option in your portal or organization to export the layer to a file geodatabase.
Use layers—ArcGIS Online Help | ArcGIS