You do not need to delete the SUF app on your Mac or Windows computer to install and operate SYSTM. However, you will need to make sure that you quit the SUF app in order for the SYSTM app to properly connect to your trainer and sensors.
The SYSTM app will replace the SUF app on iOS, so it is impossible to run both apps.
The SUF app does not exist on Android, so this is also not possible.
Note that the SUF app will cease to function on November 15, 2021. Please ensure that you've updated to the SYSTM app prior to that date.