There was a lot more I would have liked to address in depth, but I have been rightly accused of trying to turn every review into a survey of an entire subgenre. I did that a bit, but the general idea of what I call “openness” in conflict games is far broader.
One issue is when the fights actually take place. I have developed a strong preference for games that allow for a more flexible take on battle resolution. For example, in a game like Cry Havoc, the region is locked once a fight starts and is resolved later. A little more open is something like Eclipse, where there is some notion of pinning to limit your mobility, but you can still move into or out of the area before the battle starts. Honestly the fixed nature of combat timing and how closed the map can get are the things I dislike the most about Eclipse, despite the fact that I love the game (I always have to warn new players: don’t ally with all your neighbors, or you’ll end up entirely trapped by the game’s topography).
In a game like Chaos in the Old World, there is no pinning but the battle still happens at a fixed time. One of the ways in which I feel Cthulhu Wars improves on its obvious inspiration is that starting the fight is a player action, allowing for more freedom to nudge fights to your advantage as well as freeing up the tempo. This approach is also seen in Blood Rage; the quantity and frequency of battles is entirely up to the players, rather than fixed at a set number of rounds.
Relatedly, there’s a similar way in which I felt Eldritch Horror improved on Arkham Horror; rather than having a movement phase, you just make movement an action. This is a comparable design advance, turning what could be a fixed turn structure into a more fluid and choice-driven menu of actions.
All that said, sometimes there’s nothing wrong–or it might even be preferable–to have fights start the instant two hostile forces are in the same space. Kemet and Successors, as example, work precisely that way. There’s plenty of dynamism to be had in that model, too. It’s not always feasible, though–it depends a lot on how movement works, how control is understood, and other considerations of tempo.
And if you can’t have fights resolved the instant they start, all things being equal I’d rather the players be able to choose, rather than turn structure.