As a replacement for Muun, yes Phoenix is good. Whereas Muun tends to charge higher fees for Lightning transactions because it has to swap on and off chain, Phoenix charges higher fees for on chain transactions because it has to swap in and out of lightning. But if you plan to use it primarily for Lightning, then it is a good option. It does not give you a LNURL or lightning address (the email looking kind) though, so if you need that you’ll still need something like Wallet of Satoshi.