You are lucky that your devices are from Samsung, as what I described should work with recent AE device agents on most of the recently released Samsung devices, but fail for most other brands.

Screensave should be turned on and set to 30 seconds by default if you enroll your Samsung devices to AE device-owner mode.  To change the timeout to say 10 minutes (60000 msec), use the following script:

  writesecuresetting -sys screen_off_timeout_rollback 600000
  writesecuresetting -sys screen_off_timeout 600000

Make sure the "'modify system settings" permission of your device agent has been enabled, otherwise the script won't work.  In the past, configuring a timeout different from any default option available in the device's Settings will have no option ticked in the Settings GUI, though the configured value is still valid.   Surprisingly, a test I have just done on an Galaxy A71 minutes ago even have the device's Settings GUI showing the new non-default timeout.  I am not sure if this change also applies to other Samsung device models.

If  I want to disable lockscreen timeout, the usual workaround I have been using for many years is to set the timeout to be an arbitrarily big value so that the timeout will not be reached in any practical sense.  However, this does not seem to work any more.  There might be some new script command to disable screen timeout totally, but I have to do some more research.

Please note that some low-end Samsung device models released recently have their KNOX libraries completely removed from the device firmwares, and thus may not support the above.