ArcGIS Pro has a function called ModelBuilder that allows you to chain geoprocessing tools together and save them as a custom tool. Here is some documentation to get you started. If you can provide more details regarding your workflow, I can provide a better suggestion.
What is ModelBuilder?
The Join Features (GeoAnalytics) tool:
Joins attributes from one layer to another based on spatial, temporal,
or attribute relationships, or a combination of those relationships.
and its Licensing Information says that you need a ArcGIS GeoAnalytics Server license to use it.
You do not seem to be using the ArcGIS GeoAnalytics Server so I suspect that you ...
You can use arcpy.ListFields() to get all sorts of information about fields, including the field types. See: https://desktop.arcgis.com/en/arcmap/10.3/analyze/arcpy-functions/listfields.htm
One you have your list of field objects, you just query the type property, of each field object to find out its type. See: https://desktop.arcgis.com/en/arcmap/10.3/...