You have the same signature covenant ability regardless of which one you join.
Become a Draco-Lich with Necrolord, abomination factory gives you that feeling of having a pet albeit its limited to where you can take it even within the Shadowlands.
Are you a Faerie-Dragon with Night Fae, maybe go collect some of the dragon variety of soulshapes so you have your full fledged dragon form, only comes in blue.
Get your feathery double wings as an Alabaster Dragon with the Kyrian, show them how to really fly with the wings you’re born with not just given to you. Summon a chicken dinner.
Are you a Gothic Dragon dark and brooding with the Venthyr, Doors of Shadow then a sweep from the skies and a quick hover for triple movement in style.
I’m not taking my Dracthyr into Shadowlands because: It breaks lore, I’m sick of that place, I’m not making a Dracthyr, Dracthyr are stupid, none of your business, who are you? I’m playing the better, more awesome new race Sheeple !
Probably doesn’t matter they will be available for like all of 4 weeks prior to DF launch and I’d assume most people will be playing pre-patch stuff.
For the character I got rolling around in my head. His personality is very ardenweald. A little playful. But he’d also probably end up with Bastion just to help with flying lessons.