Yes, it can be or not, as an option in each table. The responsive mode is really advanced as you can define a priority for hiding columns on mobile sizes. When columns are hidden, a mobile menu with checkbox will be displayed to force the display/hide of columns.
The column size is fixed during the table edition and if you need to respect your content formatting, the responsive can be disabled on each table. If the size of all the columns is too large for the container you'll have an overflow and you'll be able to easily scroll on tactile devices.