You mentioned three (3) objectives, weight, sensitivity and taper. Starting with the easy one, taper, find what you like and buy blanks because you will find it difficult, at best, to achieve the other two, weight and sensitivity, with factory, mass-produced rods. The lightest weights will come from...

The spool shafts are small but are more than strong enough to handle any freshwater situation. However, even a very small distortion can turn a quiet reel into a chatterbox.

A simple drag upgrade should not have any impact on this problem.

Last but not least, this noise could be due to a bent spool shaft. Take the spool out and roll along a flat surface or chuck in a mini-lathe and spin. Even small problems should be apparent. I have seen this with several Pixy/Presso reels where braid was used. Good luck.

This photo has been shown quite a few times. At first, the story was that a fish was responsible for the damage, a yellowfin tuna. That story is utter and complete bullshit. Any tuna large enough to do that would have also stripped all the guides off the rod and would still be swimming with the reel.

Some baitcasting reels have a very slight wobble in the spool shaft that can drive you crazy trying to find the problem. You will not hear any sound on retrieve, only on casting due to the high RPM.

High quality baitcasting reels are not winches, be careful how you break off when snagged.

Yes, you must remove the metal cap on the original handle to get to the nut that retains it on the shaft. Replacing with a ZPI or any other handle is simple.