Main blockchain (1st layer) offers the level of safety which is similar to its core technology — Stellar. Stellar is the well-known and thoroughly researched implementation of the distributed ledger technology widely used in real-world applications.
2nd layer is also based on Stellar with similar safety guarantees. Though, 1st layer restricts 2nd layer's capabilities to operate with main blockchain to the necessary minimum. Also, Stellar makes possible "wallet-independent" applications
As other solutions with open membership 3rd layer implementations are being built with full respect to no-trust requirements. There are no financial transactions on 3rd layer, only data collection assuming that nodes may cheat. Some cheating behaviour can be detected by 2nd layer when comparing traffic records from other nodes, but basically cheating is avoided by making malicious behaviour economically unviable.