So There is still no much informations about covenants but most propably you will pick covenant, grind it and get your covenant ability propably upgrade it with grind etc.
I see problem with covenants. If they keep same gearing system as in bfa and if you can only have 1 covenant and cant switch or you will need to grind it on every switch. For sure one covenant faction ability will be good for pvp and other covenant faction ability for pve. So how should i gear for pvp if most efficient way to gear is PVE and i will propably downgrade myself for mythic raid or higher m+ key if i will play with PvP covenant ability. Same goes for pve players if they decide to try pvp. Either make PvP gear bis for PvP so i dont need to do pve or make covenant abilities easy to switch.
Also i dont like to be dragged to some covenant i dont find fancy only because i want to min max.