When you start out, you just visit the web app and "install on phone". It will use local storage but you can back up the seed words.

To create a wallet, you need a LN channel. The first receive will open a channel using a lightning service provider, Voltage API (by default). The channel open will have a pretty big fee and you need 100k sats for the minimum channel size. Make it bigger if you like.

Its beta and there is a warning about that. I haven't found any bugs. They suggest not putting too many sats into it yet.

For outgoing zaps, it integrates with Amethyst (and others?) for zaps without switching apps. I'm currently not using that feature so I switch apps to authorize zaps. I guess that adds some trust in amethyst.

For send fees, it charged me 1 sat to send 100 just now.

The only drawbacks I have so far is that you need the app open to receive. You can send from another wallet and it won't complete until you open Mutiny. I also wonder if it puts some trust in the LSP. Can Voltage steal the channel when you are offline?

Not having to trust WoS with everything is big. If you still use that to receive zaps, you could transfer back to Mutiny when you come online. I've done something similar with Alby.

I haven't tried the new zeus yet so I can't compare.

My own node is a goal, but this is a big improvement