These are both similar terms typically referred to by manufacturers to describe a final stage of charge. One could say the charger turns off or on as needed to keep the battery charged. Others may say the charger pulses states to maintain the battery at 100%.

The real subtle discrepancy is that pulse chargers are a marketing tool used by the "as seen on TV" types to promote a device that isn't powerful enough to be a charger or maintainer but is marketed as a device to desulphate batteries by using an ocillating current to break down the lead sulphate build up on plates. The concern is that if you'd charged your batteries properly in the first place they wouldn't need such a device and by purchasing a CTEK charger you wouldn't need one anyway.

Yes it's just the harmonic frequency of the pulsing which may be amplified by the surface the charger is resting on.

Yes it is the relay resetting the open circuit mode, just check the terminals are firmly connected to the battery and the noise will stop soon enough

Both of these chargers do not have the mode buttons. That's why the product codes do not start with the "M" like almost all the other chargers in the range. It also means the LED's are only illuminated once you have turned the charger AC mains on at the wall and the DC cables are attached to a battery. Once connected the half battery LED light will illuminate after a few seconds confirming the charging has started.

The charger size is best matched to the batteries Ah capacity. If you have a 50Ah battery you need a charger 1/10th the size. So 5 Amps for a 50Ah battery (MXS 5.0) & 10 Amps for a 100Ah battery (MXS 10)