Regarding to stability under capacitance load, some high end cables are very high capacitance. Like this one:
https://www.audioadvisor.com/prodinfo.asp?number=KK8PR&opt=649|655|657|660They use a lot of small wires "knit" together to get very close coupling to reduce series inductance. I have my own design by using 5 pairs of 16 gauge speaker cables in parallel and twist them together to get tight coupling. Result is very amazing.
But the down fall is very high capacitance. Mine is about 2500pF, some of those on the market can go as high as 5000pF. A lot of amps will oscillate using these kind of cables. They miss out the best cables.
Not only you have to test at least to 5000pF, you cannot use any load resistor in parallel. Speakers are like open circuit at 300KHz and above as they are inductance. So at oscillation frequencies, it's like an open circuit with only 5000pF capacitor across the output.
Also, you cannot connect the capacitor by a cable, it has to be right at the output of the amp.
It would be a whole lot easier to stabilize the amp if the cap is hook up through a cable, OR if there is a load resistor in parallel with the cap. The cable serves as series inductor and resistor that isolate the output of the amp from the capacitive load.
This is where it gets difficult in designing power amp. designing the circuit is very easy, so many different ideas. Getting it to behave is where the rubber hits the road. It took me like 2 weeks to design the compensation done.
You cannot rely on closed loop feedback to get low output impedance ( less affected by the capacitive load) because as your loop gain goes down, output impedance goes up. At oscillation frequency, you have no loop gain. The OPS determine the output impedance.