Mutiny is a Lightning and Fedimint wallet, and the answer to those questions are mostly the same as other Lightning / Fedimint wallets. What makes it interesting is that it's a progressive web app: as long as you maintain your seed phrase and aren't currently running it somewhere else, you can open the wallet using any web browser that can load app.mutinywallet.com.

Ok, so it's a disposable fedi/ln wallet ? probably useful, definitely too early.