What’s the best way to move from an iPhone 12 to an iPhone 17 Pro Max without bringing over excessive System Data?

A battery health reading of 75% after several years is normal wear rather than evidence that the phone was damaged. On the new phone, leave Optimized Battery Charging enabled, avoid leaving it in extreme heat, and use a reputable charger and cable. There’s no need to deliberately drain the battery to zero; charge it whenever convenient.

Restoring from iCloud will work, but content that already syncs with iCloud may be downloaded again after the restore. With roughly 160GB stored there, the phone could appear ready before photos, messages, and other data have fully returned. Direct transfer generally moves the existing content in one migration instead.

The current System Data total should not simply be copied as one large permanent block. The operating system starts fresh, although some settings and app data may come across. System Data can grow again over time from app caches, Safari data, logs, temporary files, and partially downloaded updates. Check Settings > General > iPhone Storage if it becomes unusually large, and consider offloading apps with large temporary caches. iOS also removes some reclaimable temporary data automatically when storage gets tight.

For extra peace of mind, keep the new iCloud backup even if you use direct transfer. Make sure important photos and files have finished syncing before erasing the old phone. You can also export especially important files to external storage using a compatible drive or another device, but that isn’t required for the normal migration.

A direct iPhone-to-iPhone transfer is probably the simplest option. Keep both phones plugged in, near each other, and connected to Wi‑Fi until the migration finishes. If possible, use a USB‑C-to-Lightning cable between them for a faster, more reliable transfer. Still make a fresh iCloud backup first, since it gives you an extra fallback if anything goes wrong.