Honestly, from what I understand:

On-chain BTC can be fully restored with the BIP39 seed phrase.

Liquid BTC is a separate network asset and may or may not be recoverable just with the seed depending on the wallet’s implementation.

Lightning BTC is tricky — channel states and balances often require additional backups beyond the seed phrase. If those aren’t saved, you risk losing funds.

So yes, your device or how the wallet handles backups can be a point of failure, especially for Lightning. It’s really important to understand the wallet’s recovery process before trusting it with large amounts or Lightning channels.

If you want safety, using hardware wallets and regularly backing up channel states is recommended.

That’s what I’ve learned so far — still learning too!