I don’t own Widex, I own Oticon OPNs miniRITE. But because my OPNs can eliminate feedback 100% (I can cover my ears up and have no feedback), I have no problem using headphones like my Bose QC3 over my ears to listen to music or anything else.
As for headset, I use the Plantronics Voyager Focus Bluetooth headset, which is “on the ear” and not “over the ear”. By “on the ear”, I mean the headset is smaller than the “over the ear” type which can cover your ear (and your HA behind your ear) completely. So it only rests “on the ear”. Because of this, the mics from the HA behind the ear cannot pick up sound from the headset because the HA is outside of the headset’s area of coverage. My workaround is simple to move the HA from behind the ear to “inside the ear” (see this pic here for reference -> ) to have it be inside the headset’s area of coverage. It works great for me and I use my headset this way for hours everyday on business calls.
With this technique, it doesn’t matter what make and model of HA you use. The only important thing is that your HA must be able to reduce feedback 100% in order for it to work. This way you don’t need to move your headset higher to line up with the HA’s mics. You move the HA down (and inside the ear) to line up with the headset instead.