Galaxy Watch sleep tracking now has dedicated toggle for REM sleep
The Galaxy Watch also has a separate toggle for enabling or disabling REM sleep recording with the latest update. Continuous heart rate monitoring will probably give you a better idea of how much REM sleep you're getting each night, because the heart beats faster during REM sleep. But having heart rate monitoring set to frequent (which measures heart rate every ten minutes) will mean reduced battery usage overnight, even though it might be at the expense of the accuracy of REM sleep tracking.
To access the REM sleep recording toggle, scroll to and tap the sleep tracking widget on the watch, then tap the three-dot button on the right and tap the Settings option. REM sleep tracking will be enabled by default once the Galaxy Watch update is installed, but you can disable it using the toggle if you wish.
