Just listened to yesterday's LUP, don't know if this has already been mentioned or was discussed during the post-show, but Google Takeout offers stuff as a collection of 2GB ZIP files for compatibility reasons, but before you Takeout, you can click that and it's a drop-down that allows you to download as a single large ZIP (if your platform supports that ZIP format) or a single .tar.gz
I've always gone with the latter, 15GB of data in like a 13GB file, done it a few times. Google Photos stuff is littered with metadata in JSON files (EXIF is still stored in the images themselves), and if you've edited stuff in Photos without saving the result as a copy and deleting the original, you'll also get both the original and edited version of all your items.
They used to put them in folders by year (and maybe also by month, I don't recall), but they don't do that anymore, so I wrote a script that gets the date from the Unix timestamp in the JSON and sorts the items that way into "year/month/date/item"

- Jivian via Matrix