Op fire filtering

[Imp]

Never deny an op fire when in good position and in range and not moved,because enemy can come in range whenever

Thats exactly why you use it instead of turning the weapon off.

It's mostly a stealthy tool for small unit's

Not really assume you are talking turning down range here.
For infantry only real time I use is if want to engage armour at shorter range but infantry at normal range.
For armour is when you use it the most.
A platoon of say 4 tanks in diffrent situations if need to do the following.
Minimum armour set above APC or IFV level for 2 tanks
Now 2 engage everything & 2 engage tanks only.

Facing nearby infantry with tanks in support set 2 to ignore the infantry so engage vehicles others leave or set to engage infantry only.

In rare cases can set overwatch hex I dont bother with as have to reset when move but can be handy at times.
Assume set tank to just fire at near targets so protecting itself but you have seen a threat somewhere. Place the overwatch & select to cover that threat in that area only.

Its like the Y key you dont use it much but it can setup a situation.