Take this with a grain of salt, but...
I believe the climb torque limits came about due to Garrett drivers setting a torque for climb without reference to itt or ng (apparently they're less forgiving), so Garrett introduced these limits so all you needed to do was look at your altitude and oat, then blindly set torque and be "certain" everything else is within limits. Cessna then adopted this practice. So, climbing generally, if your itt and ng are within limits, and your torque is below max for that rpm (208b 1865ftlbs @1900rpm) it is impossible to overtorque the engine.
Now for the g1000, if you sit stationary on a runway and apply power until the prop governs at max rpm, then pull the pitch back, you will see the red torque line increase. It's purpose is the same as the torque charts, if you're lazy and dont monitor the other parameters, as long as you dont go over the red line you should be ok. It protects your engine based on current config and conditions.
If I'm off the mark (very possible) please feel free to correct me, it's how I learn.
Cheers,
Sox