I've been playing around with different carrier builds since the release of a few mods that support a wider variety of them. However, in my testing I've discovered that trying to get support fighters to engage the right target in a fleet setting is like trying to herd cats - they just won't do what I want them to do! Support fighters with 0 engagement range (like the vanilla Xyphos, or the Roider's Dragline and Torchship's Firespitter) completely ignore Engage orders - this also extends to mods that remove engagement range, like the Bastion Carrier Core from the Modern Carriers mod, except in this case all fighters mounted to that ship will act like support fighters, ignoring Engage orders.
Here's a video to illustrate this particular issue. They try to shoot the closest enemy, whether it's a fighter that's just buzzed the command deck or some frigate off to the flank that's not the priority target. I set them to Engage partway through, but they continue targeting the Borer drones. This makes coordinating said support fighters exceedingly difficult.
All fighters should heed Engage orders - for 0 engagement range fighters like the Xyphos, ordering them to Engage should make the carrier's target their target as well, so you can at least tell your herd of cats to shoot the same thing. When not set to Engage, the normal behavior works fine.