"Drawstring closure" sounds simple, but there's a real difference between one that works and one that just looks like it does.
What a buckle actually adds
A plain drawstring cinches shut but can loosen on its own as the day goes on - things shift, the string slackens, and suddenly your bag's half open on the bus. A drawstring buckle locks the cinch in place, so it stays closed until you actually pull it open again.
Why this matters more than it sounds
The closure is the one part of the bag you interact with every single time you use it - opening it, closing it, checking it's actually shut before you walk out the door. A closure that needs constant re-tightening is a small annoyance that adds up over months of daily use.
What to check before buying
Look for whether the drawstring has an actual locking mechanism (a buckle, a cord-lock, a toggle) versus just a string that relies on friction. It's a five-second check that tells you a lot about how the bag will actually behave day to day.
Plexiana uses a drawstring buckle closure specifically so it stays shut without you having to think about it.