Neutral Link is a solid bar connection that has a removable link to enable circuit isolation for testing purposes without disconnecting the cables
Switched Neutral connects the neutral through the switch and switches on and off with the main poles. These are early make late break. This means when the switch is turned on the neutral connects before the live and when the switch is turned off the neutral disconnects after the live.
Neutral link means the neutral is always connected (unless physically unbolted) regardless of the switch position.
Switched neutral means the neutral is switched on and off with the main poles.
This is an installation question and should be answered by the end user/installer and dependent on the application.
