In vscode using Python, ctrl+F5 always asks for "select environment"
Run > Add Configuration... => Choose one of the two options.
After doing this it will no longer prompt you.
Ctrl+F5 is a shortcut to Start without Debugging What you want is just running a file according to your post. To run a python file in the integrated terminal, right-click your editor window and Run Python File in Terminal. It should open up a terminal window within VS Code and run as normal. It also takes into account the environment you are currently using whenever you run it.
To answer your other question about Python Experimental, it is an option to use the experimental debugger, an alternate version of a Python Debugger. You can read the instructions here