From the Optech write-up it's not Ark-style. It's closer to Zcash's design but posted on Bitcoin: encrypted notes, a nullifier for each note spent, and a proof that indexers check, and anyone can run an indexer, so there's no consensus change and no operator. The listed trade-offs are a one-time setup ceremony (secure if at least one participant was honest) and visible traces when entering and exiting, with peg-in/peg-out details due in a companion paper based on PIPEs witness encryption. Worth remembering that the privacy you get is bounded by who else is in the shielded pool, not by what any one transaction names.

I wrote up the ring vs shielded pool distinction here: https://cryptodecentral.co.za/notes/anonymity-set-is-not-a-ring-size

On the NWC question above, one thing worth checking with any scoped wallet connection is whose node signs the invoices the app creates. If a receive-scoped credential makes invoices from the user's own wallet, the payer's preimage shows that wallet's node was paid; with a custodial Lightning address it only shows the host's node was paid, and whether the named person got credited is down to the host's ledger. That's part of why receive-only scope is a nice least-privilege default: the app can request payments without being able to spend.