Google Takeout (takeout.google.com) should give you almost everything in one place. It's a good idea to do this periodically in case you don't get the 30-day notice. Be prepared to download a few dozen GB, though. And there is no "incremental" option.
I wanted to migrate from Google Photos to iCloud. Turns out there is no easy way how to import the photos to iCloud without loosing metadata. I gave up and just bought more storage on Google.
I'm a bit surprised that you had trouble importing photos, though. Isn't most of the metadata kept in standard EXIF tags in each file?
However, I don't agree with "remember all the different places you need to download content from". Google does this with Takeout, so I can have 1 backup of most of my things. When using different services, I need to have various backups.
Reason is: I don't depend on services giving me 30 days. I assume they can block access on the spot.
It's a questions of eggs per basket. Google wants you to keep everything in their one basket, and the result is that if they arbitrarily terminate your account, you lose everything. If they give you 30 days like OP, you have to remember all the different places you need to download content from.
If you split your services up, a sudden termination only affects a few things rather than everything, and a forewarned termination has a much smaller surface area you need to consider.