• venv and pip are included with the default install on Windows. You can use them right out of the box. Using Powershell to create a virtual environment and the subsequent directories if needed would look like this (check here for your regular CMD.exe commands):
PS C:\> python.exe -m venv C:\Projects\temp
PS C:\> &.\Projects\temp\Scripts\Activate.ps1
(temp) PS C:\>deactivate
PS C:\> 

PS C:\> python.exe -m pip install --upgrade pip
Collecting pip
Successfully installed pip-20.2.3
• Leave the generic shebang, Windows doesn't care. Having #!/usr/bin/python, #!/bin/bin/env python or whatever works for you will just be ignored by windows, no point in removing it.
• Setting environmental variables in Powershell as you would do with export on Linxu is by interacting with the $env variable. Example: PS C:\>$env:FLASK_ENV="development"