The key points are that Google Maps location history will be stored on-device, with an option to back it up (encrypted) to the cloud so if you switch devices you can keep the history. The default auto-delete will be three months, and you can increase or disable that limit.
I guess that means location history will no longer be accessible via the web site.
I don’t think Google has implemented any E2EE system for backups before (correct me if I’m wrong). I wonder how exactly this will work.