Even in 2020, email creation still requires an entirely different approach.
To get an idea why Bootstrap Studio is not made for emails and why Bootstrap itself is not made for emails, have a look at the below page. Click the “HTML button” on the right side, now compare the output on the two sides. It should then become readily apparent why Bootstrap Studio and the Bootstrap framework were never intended for email creation natively.
Maybe that tool will help you cobble something together if you want to use Bootstrap since that is the objective of the project.