It’s the same as the online check-in option, save for the extra document checks. It’s all that’s needed for when you are travelling carry-on only (which I prefer these days).

You can use the storage options at KLIA, if needed.

Note that even SQ’s Early check-in @ Changi reads as follows:
“Early Check-In Time: Up to 48 hrs before departure. Please note that baggage check-in and entry into the transit area are only available 24 hrs before departure.”