Hi Hideo,

1. Yes, I am using Python and running that on Jupyter Notebook. No, you don't need that, but you must make sure that you run using the Python environment inside ArcGIS Pro. When you install ArcGIS Pro, you will install Python altogether because of the programming language behind all the geoprocessing tools in Python. You need to use that Python because licensing issue regarding the image analyst extension you use. For the requirements, run the tools first, and if there is any library error notification, install that.

2. Previously, I worked with NVIDIA GTX 1080Ti, which has 11 GB VRAM. I believe the minimum VRAM requirement is 6GB. If you have limited cash, buy the GTX 1060 6GB, but it quite slow. And it also depends on how big the area you want to inference and how big the tiles you use to train.

Hopefully, this will help.