Best setup for comprehensive Garmin ecosystem

Hi! So some items are probably clear:

• scale and blood pressure monitor -> no decision needed
• sleep tracker --> same (you are right -> replace watch with tracker in the evening, reverse in the morning)
• Setting the Fenix as primary training device / wearable is correct

Riding:

• if you do a separate bike ride (non-Triathlon), you would record the activity on your Edge and not touch your Fenix. After the activity and sync, the Fenix will show the bike ride as well and adjust metrics accordingly (e.g. training status). If this is all you do, then pairing the sensors with the Edge is sufficient (no need to have them on your Fenix)
• if you do a triathlon or ocassionally ride without the Edge, then pair the Sensors to the Fenix as well. In a triathlon, my suggestion is to record the total race with the Fenix and use the Edge in parallel on your bike for convenience purposes. After the race you need to discard the Edge version of the ride and keep the watch one only - otherwise you'll get a duplicate which messes up metrics (can be deleted afterwards from Garmin Connect if this happens by accident)

Heikoo said:

Setting the Fenix as primary training device / wearable is correct

Except if you want the more accurate Active Calories from Edge 1050 to override those of Fenix 8. If you keep Fenix as the Primary Wearable and Primary Training device (PTD), Active Calories from Fenix will be used, and the more accurate Calories from Edge will be discarded. Only if you set Edge 1050 as the PTD, Active Calories from Edge will be used. 

See also Garmin Connect: Setting Your Primary Training Device | Garmin Customer Support

If you record data from multiple Garmin devices simultaneously, your Primary Training Device will provide the active calorie calculations.

Another possibility to record activities with watch/Edge combo, is recording everything with the watch, and using Edge just for navigation, and/or as Extended Display of Fenix. Many users prefer this way (and personally, I would rather recommend this method, too), since it avoids diverse problems with the data synchronisation between the devices. Getting the Training Status / Physio TrueUp into sync is not always straightforward, if not done carefully (it requires two cycles of syncing both devices before and after the activity). Also, there is still some metrics that is not synced over Physio TrueUp. And unless the watch records an activity, the HR sensor is in the less accurate low power mode, recording only 2 minute averages, and all metrics it measures is less accurate. 

thanks for the additional perspective - seems i was not aware of some details.

• my assumption would be: When i record a session on the Edge, then for this particular period all metrics from the Fenix (being idle, low power HR mode) are overridden by the session data from the Edge. Apparently that's not the case?
• i think this all depends on how important this is for the athlete. For me, the Physio TrueUp and Training Status *seems* to work reasonably well with my setup and it's hassle-free (use the watch for swim/run, use the edge on the bike - done). So it's acceptable e.g. the calories may be a bit off (according to your explanation). For evaluating my training i rely on other concepts such as TSS (TrainingPeaks)

Performance / training related metrics is synced well. Calories can be handled properly if you set the Edge as PTD. Other metrics not shared over Physio TrueUp, is mostly irrelevant (i.e. Stress not measured during most activities anyway) or unimportant, or the support was added recently (i.e. Body Battery). So I'd tell both methods may work well, as long as you have the devices properly configured, understand how the system works, and take care to have the TS properly synced before and after each activity. So indeed, it is rather a matter of personal preferences.