Cavalry Team Insight

I run eldigan (ward cav), camus (goad cav), frederick (hone cav) and Brave lyn.

Sigurd or Siegbert are your best bets on red. Sigurd's Boon allows him to hit 45 speed running Swift Sparrow and Hone buff. Siegbert will hit a bit harder, but will be much more frail. Both can run DC if you want them to, though I'd suggest giving them Heavy Blade Seal and Aether if you do.

Reinhardt. All the Reinhardt. Unless you want a speedy tank, then go Camus. With Fury and full buffs, Camus will have 42 speed and great physical bulk, great for baiting.

Gunnthra with full buffs and Gronnblade. With her unique B and better stat spread, she edges out Cecilia. I suppose LA!Lilina could also be used, I'm just a really big fan on the debuffing Gunnthra provides, while still killing things with full buffs.

B!Lyn. Try running her with Brave Bow and Support. Though, I feel a healer would be equally as good, if not for very different reasons.

The definitive horse emblem is pretty much Sigurd, Cecilia, Reinhardt and B! Lyn, and you have perfect IVs for pretty much all of them (though Sigurd can work with pretty much any IV set).

That's your base. Then you should mix and match depending on the scenario (I swapped Lyn for Eirika for some of the GHB Elite quests).

I assume you wanna use it for PVE? I wouldn't invest much further into them for Arena, because of abysmal BST and scoring potential (I actually regret my lone Sigurd merge).