Brushless motor are rated in similar terms to the brushed motors.

Kv - is the amount of RPM the motor will produce from 1 volt with no load. A larger value means more RPM's from a given voltage at the loss of torque.

A 540 motor represent the can size. A 540L motor is about 61mm long where as an XL motor is 72mm long. The SV motor is 56mm long and would be best classified as a 540S. All 540 size cans are 36mm in diameter and have 25mm bolt spacing c to c. The larger the motor the more torque the motor produces. Again it will be at a loss of RPM when comparing turns.

If you wanted to run a Feigao motor on 29v or 24 cells, I would recommend the 540 14XL. I haven't ever ran this setup so I would recommend starting with a 40mm prop and then working your way up.
This setup will not be a rocket in a 41" hull, I personally would go with a single Lehner motor. But then we are talking high coin.

Ryan