Horse Emblem, what to use?

Camus works well on most maps due to him negating his cavarly status in effective weapons via A skill, most notably against Ursula as he has DC and Granis Shield.

Xander is good to take out Michalis as he has WTA and Guard, to slow down the process of activiating his special. Brave Lyn is useless in taking ou the boss on the same map as he has Iotes Shield

Eirika and Catria work well together as the latter the latter will debuff the highest res unit, making the former kill units faster with Glepnir.

I use horse emblem almost every time to complete Infernal GHB and my team always consists of Reinhardt, Brave Lyn, Sigurd, and Azura (any dancer can work). Reinhardt can destroy pretty much anything and Brave Lyn with a Brave Bow+ does the same. Sigurd serves as the tank and Azura serves as a dancer to allow my Reinhardt or Brave Lyn to get more attacks or for re-positioning.

Every now and then though, I switch out Sigurd for someone else. Sometimes I need a more offensive Sword unit, so I switch Sigurd out for Siegbert. For your case, Sword Reinhardt, Exalted Chrom, or even Brave Roy can replace Siegbert as an offensive Sword unit.

The horse emblem team I use does not always work, because sometimes a certain unit doesn't do damage or is useful in the map. For example, in Kana's infernal map, I swapped out either Performing Azura or Brave Lyn for my Nowi, because they weren't contributing enough for me to win. Yet, I will say that horse emblem is very powerful and can help you complete most if not all GHBs on infernal mode.

I use Xander, Brave Lyn, Reinhardt, and Cecilia/Gunnthra. You could swap Cecilia/Gunnthra for Lilina.

Xander uses Distant defense A skill, Quick Riposte, Bonfire, and Hone Cavalry. He supports best with Lyn, and I summoner support him on hard challenges.

Lyn uses Brave bow, Luna, and Fortify Cav.

Reinhardt uses Death Blow, Luna, Lancebreaker, and Goad Cav. You have a Catria though, so you could give Reinhardt Chill Res instead of Lancebreaker.

Gunnthra uses Death Blow and Glimmer. Cecilia uses Triangle Adept, Iceberg and Bowbreaker.

All use reposition except Cecilia who has draw back.