The fighting at that time was primarily face to face. In the 18th Century, 2 armies stood shoulder to shoulder with rifles and muskets. It was basically a number game as it took almost 100 seconds to load the second shot.
Propellant chamber was 8” long with a diameter of 3” and capable of carried 1pound of gun powder. Being made of iron, they could develop humongous chamber pressure which gave them their famous 1mile range. The stabilizing rod was replaced by 2 feet long metallic blades.
You must have read accounts of 100 year war where the sky turned dark due to the showering arrows from English longbow men. Now (18th century) soldiers rarely carried shields or wore armor to protect them and instead of pointed arrows there were now swaying blades which slashed everything in its path. I do not want to even imagine the psychological effects of these flying scythes launched by invisible enemy. The metal chambers also exploded spreading incinerators all over. These ignited gunpowder arsenal near the cannons and sometimes even the gunpowder kegs tied over the abdomen of soldiers.
English longbow men rarely got a chance to fire their 5th arrow, while each one of the Tipu’s soldiers could launch 20 rockets simultaneously. Then they used to move to the next rack of rockets.
You might be tempted to compare it will a cannon. But cannons are heavy and are slow moving. They are few in number and expensive. This severely limited their effectiveness. You cannot ambush with a cannon, because they can be reused by the enemy.
On the other hand march 5 horsemen and set up a temporary rocket stand 1 mile away from the enemy camp. Fire 100 rockets and run away. I bet most of the surviving enemy will spend the rest of the night glazing towards the sky. An army which has not rested cannot attack.
These rockets were build during 1750, and the next generation practical rockets were V2 (WW2 1940). We had 200 years of technological lead.