If you look at basic zergling vs zealot combat in SC1 vs SC2 you'll see what I'm saying. In SC2 they almost move like liquid and they don't form accidental choke points. The fight is over much faster and simply rewards the beefier army.

https://youtu.be/xPC8aIl7nek https://youtu.be/mLr1co1f5-c

For example in Warcraft 3, which is much smaller scale with 10 - 20 units per player at any time, players constantly look for ways to block each other. While the fight is happening you might sneak a unit around just to block their path when they escape. This wouldn't be possible if the pathfinding was better at steering.

https://youtu.be/2GCpjpIuSII

In terms of terrain maybe land/sea/air in Red Alert 2?

The more tactical RTS like Company of Heroes and Dawn of War 2 use the terrain a lot, but in small scale ways like moving from cover to cover and building to building. The terrain is very complex there.

The new Dune Spice Wars only has desert but it has some interesting ideas about movement. It's a much slower RTS and has been described as real time 4X.