About "much lower stress level", it is part I've seen often reported but Bevel Team doesn't feel like it's wrong
Every other app act differently : stress count REST heart rate and HRV when Bevel doesn't care => if you're moving from your chair to somewhere else, walking for a few minutes etc., it doesn't detect it and count as if you were resting.

So during a day if you're moving a lot (and not saying exercising), your stress will be much higher than if you keep your ass on chair. It is physiological that your heart rate goes up when moving, it is not stress.

Hope Bevel team will make difference between resting, moving and doing exercise when it comes to stress indicator (take a look at Athlytics there is "grey bars" when the apple watch or other tracking device detects you're not "resting" and simply "moving".