I have a Python 3.6 script that I want to turn into a tool for that I can use in ArcMap (10.5). Will that even work or will I strictly have to do it in ArcGIS Pro?
I couldn't seem to find any documentation on this.
All you have to do is make sure the Python code is compatible with both versions
3.x. The six module has many utilities that help with writing forward and backward compatible code while maintaining best practices (use of iterators, etc).
One thing I am not sure about is whether or not you can use the same
.tbx file between ArcMap and Pro...I'm assuming you can as long as the underlying Python Script tool code is compatible. Of course, a Python Toolbox would probably be the best solution to work with both.