Could I have some tips on a potential flier team?

I would go Speed+3 on S!Corrin to help w/ doubles, Iote's shield for Myrrh is fine already, Distant defense for +10/+10 on Grima if you're using her as enemy phase
Probally Attack+3 on Ellincia since shes -Atk already and needs the extra dmg to take out some of the bulkier greens and kill a few extra red units. If not that, Quickened Pulse+Moonbow functions a lot like Reinhart for a quick turn 1 ORKO
Also you may want to consider running Glimmer on S!Corrin. Glimmer and Moonbow are usually the same, but I find that Glimmer Proc on my F!Morgan is often enough to take out some Arena threats like universal breaker Hector in one hit

Your Elincia, S!Corrin, and NY!Azura are pretty much good to go. I would recommend scrapping any fortify/warding bonuses with this team as it's a heavy offense team, so capitalize on that. Add another hone or goad on Elincia instead. If you're lost for seals, just try any of the +3 stats, we have up to 2 or 3 of each kind now (basic +stat, Initiate +stat, and Squad Ace), so +3 Spd or +3 Atk for everyone. Hopefully you completed Tempest Trials back about 3 months ago, they gave Iote's Shield as a seal for a reward. That would be good on any of them, but best on S!Corrin most likely so she can take bow hits and retaliate instead of dying. If you find yourself initiating most fights with S!Corrin since she is ranged, consider Spd Smoke for a C skill to help in Elincia's quad attacks. Another potential load out for S!Corrin is:
Weapon: Blarraven
A Skill: Triangle Adept
B Skill: Bow Breaker 3
C Skill: Goad Fliers
Seal: Iotes Shield

This is a crippling anti-bow build that may even allow for survival without Iotes Shield. Triangle Adept gives a bonus to 2 colors in this case, vs red AND vs colorless due to blarraven, just make sure she avoids all greens. If you do run Triangle adept on NY!Azura, take care against reds. My personal preference is fury on dancers, as I use them primarily for dance, attacking only when I absolutely have to, thus the passive +3 to all stats just helps out BST overall WHILE increasing defenses and offenses and lessens the blow from red units if it happens. I've seen scary Myrrhs (probably 10+ merged now that i think about it) that are so specialized in def, they can take a bow hit no problem. Combined with her weapon, not a single bow user can match her def and thus can not follow up and finish the job. So you may not need Iote's on her, swapping her seal for either Distant Def or Close Defense instead.Your A and B skills for Myrrh are right on the money, but I would consider swapping Aether for a shorter charge, more powerful ability such as Ignis or Bonfire(this one most likely). Also if you do chose Myrrh over F!Grima then I WOULD recommend one of your members having fortify fliers to boost Myrrh's def as much as possible. I'm not too familiar with F!Grima yet, but her take away definitely seems her weapon combined with her A skill. Having her +Spd is good, especially when she is buffed by hone/goad. Vantage is a good choice for defensive phase, Desperation works well for offensive phase. Any chill skill would work nicely on her too but those are super rare, expensive, and fodders a really good hero. I happened to witness and really like the idea of a dual smoke on her, so Seal: Atk Smoke 3 and a C: either Spd, Def, or Res Smoke 3 (probably Spd Smoke is best to help lower enemy teams' speed to help proc quad hits with Elincia). She has decent def for a flying unit, but it isn't that strong, especially when not merged, so I would recommend moonbow over ignis. Also, Reposition is a fantastic ability overall and could be used on all but NY!Azura, obviously. Drag Back works similarly as well I suppose, its all about positioning your units. The strategy which I had discovered in the challenge maps was basically, send in a buffed Elincia, kill a unit, dance her, kill another unit, use one of the fliers to reposition Elincia, use the the final flier to reposition dancer/original repositioner. Rinse and repeat. Hope this helps.