Apple Watch SE and sleep tracking, plus a quick question about exercise tracking too!

I am no apple expert, but i have an SE watch (and an iphone), so I can attest to these comments:

1. re: exercise minutes - generally, you have to select and start a workout in the workout app on watch in order to record your intended activity as exercise minutes / workouts.
2. re: activity app progress on watch - you should be accruing move and stand data as long as it is setup correctly - i.e. paired w your phone, permissions enabled on both devices for motion sensing, etc, goals and stats entered into activity app, etc. The watch setup should walk you through these things when you first turn it on, as will the watch’s activity app when first opened. You probably have that all covered already, though.
3. The red / move ring progress is earned by any activity at least equivalently (or more?) challenging as a “brisk walk.” Stretching might not cut it, and it definitely won’t trigger the workout detection notification that might prompt you to start recording a workout (another setting you must enable) in order to earn exercise minutes - tbh, this feature does not detect many types of “workouts” and rarely does so even when I am intensely engaged in any of them, in my experience. Sadly, not a reliable feature on either watch i have had (se and series 7). The workout app includes a flexibility workout setting, as well as yoga, pilates, and various other workout selections to track natively w the watch. Can’t say many of these workout options offer much activity-specific calibration or stats, so you will need to have the gps enabled during the workout in order to obtain the most accurate data points.
4. The watch connects to the phone via Bluetooth (even if both phone and watch are connected to wifi, I believe), but i was under the impression it would record sleep data w/o requiring connection to phone, deferring export of data to health app until phone was connected. Airplane mode w both wifi and Bluetooth disabled should not prevent sleep data from being collected by your watch. You will need to set up your sleep schedule, sleep focus, etc in order to cajole the watch into tracking sleep when you want it to. You should be successful if your sleep and wake times irl coincide w your predetermined sleep schedule in the app and provided sleep focus is engaged when you go to bed and remains on throughout your sleep session. Would not expect any additional tracking to occur if you snooze or sleep in beyond the allotted period. Fall asleep w/o adherence to any of these parameters? Well, good luck getting any data from Apple’s integrated sleep tracking.