I would not call it a token. Cashu is the protocol.

So cashu is chaumian ecash protocol on bitcoin.

It works like having receipt of bitcoins that you store at a custodian. You can either put in more bitcoin and mint more ecash, or melt your ecash and get back your bitcoin. But this is done in a private way.

I think the USD cashu is solved also with btc. It is not connected to the legacy system on that regard, or there is also such?