Perhaps it would help you if you knew the formulas for damage in EVE:
There are 3 components to the performance of weapons, and this “performance” is recalculated into damage. That means, for example, that if your gun would miss in a real life situation (with fully realistic physics) 50% of the time, the game recalculates that into a simpler physics simulation and just gives you 50% damage on that gun. So, the 3 components described below translate into reduced damage for your weapons, rather than notifications that you miss or that the target evaded, etc.
The 3 components:
Range. Your guns will do 100% of their rating in damage from 0km to their listed Optimal range. Missiles will fly and hit targets from 0 km up to the maximum range dictated by their flight speed * fuel flight time. Drones will function within their control range, then if the target drags them outside, you’ll lose control. For guns, once the target gets past the Optimal range, damage is reduced linearly (half damage at Optimal + Falloff, zero damage at Optimal + 2Falloff).
Tracking. Your gun turrets need to track the enemy ship, and if it orbits you very close and very fast, the angular orbit speed may be too high for the guns to track. For missiles and drones, if the target is faster than the missile speed, the missile won’t “catch up”. All 3 weapon systems do full damage as long as they can track, and, again, if they can’t track, reduced damage based on how poorly they’re doing at tracking.
Size. All weapons have a signature resolution, and all ships have a signature size. This refers more to how big their dot appears on a “radar”, but because the game simulates things based on “signature”, in effect the signature radius of a ship IS its size. Big weapons cannot achieve direct hits on small ships, so the effect is that a big weapon will do very little damage to a “small” ship, even if it’s sitting still. A big weapon will do full damage to the big target it’s intended for, of course.
So, all three of these things result in 100% damage or reduced damage, and when you combine the graphs for all three, you get a bell-shaped curve of max damage at around the Optimal range for most guns.
But, these 3 different weapon calculations also answer your questions about the various electronic warfare devices you asked about:
Tracking Computers increase the tracking of guns, so that you can hit close, fast orbiting targets a bit better. Or they don’t increase tracking, but increase the range of your guns, for hitting further away.
Target Painters make the enemy ship BIGGER, so bigger guns and missiles will do more damage to it. A target painter won’t do anything if you’re shooting light missiles at a battleship; the target is already big enough for the missiles to hit. However, if you’re in a battlecruiser with heavy missiles and trying to shoot heavy missiles at a pesky small frigate, a target painter will make that frigate take almost full damage from your heavies, even though they’re intended for cruiser-sized targets.
EDIT: As far as “how does the 10% compare”, it compares based on the situation. Are you trying to track an enemy that’s orbiting you very close? Then a tracking script will be excellent. Are you trying to shoot big guns at a small target? Target Painter will be awesome. Are you trying to shoot a target that’s kiting you, hovering just outside the range of your guns? Then a long range script (and long range ammo) will be good.
Sensor Strength affects how easy it is to probe things down. Signature Radius affects how long it takes for big ships to target-lock you, and also damage resistance if you have big weapons shooting your small ship.
Keep in mind that destroyers are designed to kill frigates, and they are so “designed” in the following ways:
Frigate-level armor and shields, frigate-level weapons. Destroyers will easily resist a frigate’s damage, while being able to overwhelm it with more guns.
Big signature radius compared to frigates. A frigate will take about half damage from cruiser-sized weapons (esp. missiles), a destroyer will take full damage. Combined with “frigate-level armor and shields”, this makes the destroyer very vulnerable to cruisers. That signature radius reduction on the T3 cruiser is intended to help you survive enemy fire, rather than avoid detection, IMO.