Hy!
Currently I'm using my Fenix 7X SS with a Jabird Vista (v1). It had connectivity issues (random disconnects during workout) with my previous Fenix 6X Sapphire since ANT/BLE/BT 6.XX firmware released, however it works flawlessy with other devices like my phone, tablet, notebook... So Garmin has changed something 1,5 year ago in their BT firmware that made the connecting with Jaybird Vista (v1) unreliable.
I'm about to buy a new headphone for running, but I think it would be helpful for every user to see which headphone works stable with the Fenix 7 series.
So if you have a reliable operation watch + headphone combo, don't be afraid to share it.