What to use for neutral protection
It is presumed that your question refers to overload / short-circuit protection for the neutral conductor.
Should the cross-sectional area of the neutral conductor be equal to or greater than that of the line conductors, no specific protection for the neutral conductor would be required as that would be taken care of by the protection provided for the line conductors.
Should the cross-sectional area of the neutral conductor be less than that of the line conductors then specific protection for the neutral conductor would be required.
Neutral conductor protection would be similar to that provided for line protection (e.g. MCB), but sized according to the cross-sectional area of the neutral conductor.