Some detailed Unified training Status would be appreciated

Agreed there needs to be more guidance: something like a reasonably detailed blog post with a few worked examples.

In the meantime, I suspect/assume, the device selection for both primary wearable and primary training device only becomes important either a) if there’s a direct conflict, b) if multiple devices process data using different versions of protocols (remembering a lot of calculations are still made on-device and not all devices, especially legacy, will be using the same latest and greatest) thus one consistent set of protocols will be used for trending.

In practise, reckon this comes down to using common sense in selecting the primary devices per used most often for their intended purpose, which in turn should reasonably mean these devices are connected / exchange data regularly (a requirement for the data to line up), along with attempting to keep your devices updated to a similar software level (if possible) for the best results. Specifically, until these elected devices have done a “double sync” (ie. once to receive inputs from other devices/sources, then process, then sync back to Garmin Connect) the data on Garmin Connect might not be accurate, and in turn will then need to onwardly sync to all other devices. Depending on the device, it’s power state and connectivity, this might happen automatically in near real time, regularly or periodically. 

But why is my fenix watch giving 0 hr recovery, even after heavy work outs  with my edge 140..

I wear my watch all day… not my edge…

i stand corrected…. it is the first time for the last 4 edgeworkouts that the recoverytime is now also mentioned on my Fenix… there is hope!,,,,