So two hops, basically. First hop sees your IP address but not the website you're going to, second hop sees website but not IP address. Similar to Private Relay: https://support.apple.com/en-us/102602.
Very true, but if even 1 of (Obscura, Mullvad) is honest, there's no de-anonymization.
For traditional Single-Party VPNs, you just need to compromise 1 party, with Two-Party Relays, you need to compromise both.
Just Obscura's compromise is enough, as pointed out previously: https://news.ycombinator.com/item?id=43016574
Unless something has changed in Obscura's architecture, the interface with Mullvad is under Obscura's control, and thus it can compromise client's credentials. This is unlike iCloud Private Relay where the guarantees are cryptographic in nature and not merely based on promises.
Yup, exactly!
Yup! Mostly less changes on Mullvad's side. Also QUIC has less overhead than MASQUE by definition.