One thing I find interesting with Engage is there will be a lot of variation in which emblem players prefer for Alear. I generally stuck with Lyn, as it made their speed so high that enemies struggled to hit me at all, even bosses. I used their special bow attack to pick off either an archer or long-range caster in a tricky position, and their doubles ability to run forward to bait bosses, call up the duplicates and watch the enemy just flail at them while I shot them to bits. It’s a great ability for choke points too.
Corrin’s terrain abilities were another choke-point hero, as was Ike’s Grand Aether (and how Ike makes the hero they are paired with an absolute unit). Towards the end I leaned on those three a lot to control the battlefield, but Lyn stuck with Alear all the way to the end.