Good question! Most unblocked versions of browser games like Drift Hunters are usually the same as the official version, just hosted on different platforms that aren't blocked by school/work filters.
Regarding your save data concern - you're right to worry. Many browser-based games use localStorage to save progress, which means if you clear your browser data or use a different browser/device, you'll lose your progress. That's one of the trade-offs with browser games.
If you're looking for reliable browser games with better save systems, check out HoodaMath.com - they have a huge collection of unblocked games (including racing and other genres) that work on school networks. Since it's classified as educational (.com domain helps bypass filters), it stays accessible. Many of their games have cloud save features if you create an account.
As for updates - it depends on who's hosting the unblocked version. Established gaming sites tend to keep games updated, but random mirror sites might not.