The python window or notebooks in Pro have full access to python 3.7 and a large number of standard python modules, plus all that arcpy offers and full access to the standard toolbox tools and any others that you are licensed for (eg the Spatial analyst, Network Analyst, Image Analyst etc)
Although the course says it needs pycharm, it is simply a python IDE
In the course called "Python for Everyone" it says this:
"If necessary, IDLE can be used to complete this course. However, please note that exercises steps are written based on PyCharm.
After installing PyCharm, the Edit With IDLE (ArcGIS Pro) context menu option associated with PY files might not appear. If it is necessary for you to use IDLE, you can access it by opening File Explorer, browsing to C:\Program Files\ArcGIS\Pro\bin\Python\envs\arcgispro-py3\Scripts, and double-clicking idle.exe."
"Idle" has a primitive user interface but does have the basic features of an IDE including a debugger. Trust me, you will want to use a debugger! Pycharm is not free, personally I use Visual Studio Code and lots of other people here use Spyder. I think both of these are far better than Pycharm. Good luck in your python endeavours.