I've been picking up some fights now in Horizon and I find some things frustrating...
My ships "see" enemy ships in adjacent sectors that I don't see while in tactical mode (maybe an indicator (red arrow or something like that) in tactical overview would be helpful to show that there ist more in the vincinity).
The automatic mode only knows one strategy at the moment: attack. Just attack, no matter how the odds are and where it is.
So I find troop transports with virtually no offense weaponry chasing enemy cruisers, even motherships!
Only way to avoid this is to micromanage every step and try to retreat. Because both sides have about the same speed, this goes over multiple turns.
Either I change to auto mode which would result in the transports committing suicide or I can spend an hour or so to manually guide them (and the reinforcements) to save them from their fate until said reinforcements arrive. Setting a course away from the enemy ships is also ignored. They attack.
Back on the galaxy map, I tell the transports to head to the next base. Result: they ignore it and go on "chasing" cruisers which happen to be in the neighborhood.
It's like herding mice with a couple of cats straying around.

When I see the size of a sector, the travelling speed of my ships and the weapon range, I can completly hide 3-4 fleets in the sector without ever getting into mutual support range (not in a reasonable amount of time). Comming for help is quite useless atm until you can say your ships not to attack and try to flee in one direction. Even then, it takes several turns (turns, like in "I have to press the "next turn" button") until the helping fleet comes to weapon range.
My view is that while in combat, the sectors are quite irrelevant. All happens at the same time in different places. My problem with this is that the combat view switches (randomly as it seems) between the sectors where fights take place, so I loose the general view completly. And because the fleets are so scattered when travelling more than 2 sectors at a time, you never know where they will end up.