If you think of it as a level thing... troops on the front line wont be too worried about targets 90 to 120km away, but they will be worried about the troops or armour formations forming up to attack them that are 10, 15 or 20km away.
In which case the 122mm Grad would be the vehicle supporting them and they can use that out to about 40km with some rockets.
Interestingly the sensor fused top attack munitions for killing tanks and armoured vehicles fits two munitions per 122mm rocket which can reach to 30km.
A Grad vehicle has 40 launch tubes so that is 80 top attack anti armour munitions with a flight range of 30km.
Incidentally the old 9M22U Grad rocket with the single 18.4kg rocket has a range of 20km, but the newer 9M521 has a 21kg HE warhead and a range of 40km, while the 9M522 has the heavy 25kg warhead but its warhead separates in flight so the reduced drag means it can reach 37.5km despite having a bigger warhead.
The 9M217 is the sensor fused top attack munition with two munitions per rocket and 30km range, while the other standard rocket is the 9M218 which has just dumb HEAT submunitions and a range of 30km. The 9M218 makes up for lack of guidance by having 45 munitions in each rocket.
The interesting thing is the 300mm Smerch rockets the 9N152 rockets, which are the top attack submunition warheads are carried in loads of 5 per rocket, which means the Grad can launch a volley of 40 x 2 = 80 per vehicle, while the Smerch fires 12 x 5 = 60 per vehicle.
Obviously the Smerch can launch them three times further, and of course the Smerch rocket with the HEAT bomblets for top attack (unguided) each carries 646 bomblets per rocket, so Grad launches 45 x 40 = 1800 top attack unguided bomblets per vehicle volley to 30km , while Smerch can launch 646 x 12 = 7752 bomblets to 90km.
Now line up 6 vehicles and launch a volley and you can see why they are considered so useful.
The different sized longer ranged rockets become more relevant at higher levels... when you get to 450km range Iskander in many ways you could use that to attack targets deep in the enemy rear without having to risk helicopters or attack aircraft.
A well defended target might warrant launching several Iskanders to defeat air defence capability before aircraft go in to finish the job.
These weapons are artillery and not strategic as such.