I had a very bad experience with my BT headphones so far:
JBL Inspire 500 -> Bad in any way and doesn't work wit fenix (dropouts)
Vivianco Outdoor -> basically not bad but doesn't work with fenix (dropouts)
Samsung Galaxy Buds -> Best headphones of all time but sadly also dropouts with fenix
Now I bought JBL Reflect Mini 2 and they work absolutely flawless with the fenix, no dropouts at all and for a price of about 70€ very solid headphones with good sound and absolutely stable in the ear during workouts. If you don't mind the cable and don't want to spend too much I can totally recommend these. The previous model is also on the (very short) list of Garmin recommended headphones.
Check it, these are the best alternative of airpods. protechbound.com/.../