No worries, appreciate you setting up the unofficial ORK discord channel too!
#1. I believe this was added in XCOM 2 as a heavily user requested feature. An example would be if your combat has "Attacks of Opportunity/Sub Actions" that trigger when a combatant leaves attack range, IE walks by an enemy combatant within 1 tile.
If you have your grid movement set to find the nearest path in most cases you will walk by that enemy and trigger an AOO attack. You could of course, just allow movement as many times as you want and move tile by tile but this feature will essentially allow you to plot "waypoints" so you can navigate obstacles provided you have the Action Points/Movement for it.
Furthermore if you decide to have enemies that have a AOO range of more than 1 tile, say 2 (polearm user) or "traps" from grid cell effects you might want to consider this too, especially if you are using the XCOM 2 action system.
It's a QoL feature, allowing you to adjust the pathfinding for grid movement. When you are clear of enemies you can freely move and find the nearest path, when you want to avoid an enemy/trap you can plot waypoints for an alternative path around the enemy/trap seamlessly without having to move tile by tile.
#3. I suppose to easiest way to explain is that it would be an in editor time saver.
Scenario 1:For example, let's say you want to define a group of 3 combatants.
Combatant 0: Bandit Thug
Combatant 1: Bandit Thug
Combatant 2: Bandit Thug
Now within the editor, you could "randomise" it by defining variables for Combatant 0 but you would then also need to define a 4th combatant if you wanted to always keep it a group of 3.
Combatant 0: Bandit Thug (Bool Off)
Combatant 4: Bandit Leader (Bool On)
The more combatants you want in your group, the longer your list is gonna be.
With this feature, within the position of Combatant 0: You can define Bandit Thug, Bandit Leader, Bandit Captain, set a chance for it to spawn or a variable requirement, define a fallback combatant (similar to conditional prefabs etc).
Scenario 2:Combatant Spawners. The difference is you wouldn't need to set up multiple pre-defined groups for achieving the same thing. That is, if your goal was to spawn a group of 3 bandits, with the chance of spawning a bandit leader.
1st Group:
Combatant 0: Bandit Thug
Combatant 1: Bandit Thug
Combatant 2: Bandit Thug
2nd Group:
Combatant 0: Bandit Thug
Combatant 1: Bandit Thug
Combatant 2: Bandit Leader
So rather than enabling "Spawn Random" to select between the two pre-defined groups, or defining variables, all the "randomisation" would be done within the editor.
When done within the editor it would reduce clutter when trying to define all the groups within the combatant spawners, give you more control with variables IE if you want to introduce a specific enemy late game within an easier group etc. Otherwise, as far as I can tell you will have a very long list of combatant groups to sort through.
Scenario 3:Battle Component. Let's say you handle the combatant groups here. You could define requirements for each group but in my cases, I have "battle maps" were fights with multiple different factions can occur, stronger enemies being introduced depending on difficulty etc, it results in a very long list.
Closing:It would basically automate all the manual steps you have to do to set up randomising groups and all defined within the editor and reduce the amount of clutter. I think a feature like this would lead to a lot of flexibility.