Hi,
1, Add custom class in row or column or any element has support input "extra class name":
- in column: http://prntscr.com/msvqh0
- in row: http://prntscr.com/msvpsn
2, Add custom style css for custom class:
- For Redux Framework - Theme Options: http://prntscr.com/msvosq
- For Kirki Customize - WordPress Customizer: http://prntscr.com/msvpgm
3, Also, you add CSS Media Queries for custom css:
https://www.w3schools.com/css/css3_mediaqueries_ex.asp
Thank you