The 5.5.0 release of Terminal (4th Jan 2020) added the option to toggle Natural Copy/Paste in the Settings menu: https://github.com/elementary/terminal/releases/tag/5.5.0
So now you can change this via the UI.
This was also mentioned in Elementary's blog: https://blog.elementary.io/hera-updates-for-january-2020/#terminal
When opening any application throw terminal the process will the linked to the terminal that opened it.
But you can disown the process that opened the terminal and then close the terminal without affecting the application by using the following syntax when opening the application throw terminal:
webstorm & disown
Syntax using with webstorm as example.