What Size Should I Choose for Takeout Zip Files?
Choose smaller parts. They download more reliably, and reassembling them is the tool's job, not yours.
Google offers sizes from 1 GB up to 50 GB. Bigger sounds simpler, but one interrupted download wastes the whole file, and large zips are slower to open on a modest computer.
2 GB or 10 GB parts are the sweet spot. Each one downloads quickly, a failure is cheap, and you can start working before the last part has arrived.
Takeout JSON Metadata Fixer takes every part at once and treats them as one library, including photos whose data is split across two zips. It runs on your own computer and is free for your first 500 photos.