I don't know where some of this info is coming from??
To start with you can get a mechanical fuel pump with a 200 gph for GM motors This bolts to the block and runs off the eccentric cam. This will handle any 500+ cubic inch with the correct fuel line size. I do like an electric fuel pump over a mechanical one because of pulsing that happens. The fuel pressure is more steady with electric rotary fuel pump.
90% of the time when an electric fuel pump fails is because of either bad fuel, running the gas tank on empty if the fuel pump is inside the gas tank, the pump needs the gas to help cool the pump, this extend the life on any in the tank pump. Not changing the filters every 15k miles or poor contacts. I have seen the screen in the tank full of dirt and collapes. No ideas where it came from. Going to a gas station that doesn't change the filters at the pump also cause failures. I have an electric pump with 122,000 miles on it and it still work fine. I have had mechanical pumps on SBC motors and had new one go bad a 20K miles and one live to 144K miles. The diaphragm wears out over time and the gas leaks from the little hole in the top of the pump. This is a case of being lucky or not. Both can live for 100K without failures.
Braided SS line come with a couple of different liners in it. It depends on what fluid you are running through them. Are the lines a pain to make, a little but if done right, no failures. Measure twice and cut once, most people ball park it and leave bends, pinches, rubbing spots, no mounting clamps for the line, long runs to a vibrating source like the motor. These all cause failures. The liners come in a couple of materials, Rubber,
synthetic rubber, nylon, teflon, and CPE. You have to use the correct hose for the correct application.
Fuel pump kill switches, they also depend on how they are setup to work. Some switches work with a roll over, some work off a "g" force decellerometer. to cut off the fuel pump. The side effect of this is even if the fuel pump stops working you can have up to 60 psi of pressure in the lines. Line breaks and you have a line with quart of fuel to blow all over the place and light up. If you are using teflon tape on lines, first off there is a tape for fuels and oils only, it's not WHITE, Pink or Yellow. One doesn't work with all applications. If there is teflon pieces in the carb bowls, someone used the wrong stuff or too much was rapped around the threads. There is also a boiler cement that works best to pervent fuel or brake fluid leaks. When couplers are torque to the correct spec, there should be no failures or leaks. At this time this is the best info I have on a couple of the questions. Rick L.