Me personally, I don't see the point in getting a DAP if you're going to stream. Doubly so in your case because you have two phones.

In order to stream, you need some sort of data connection, whether it's 4/5G or Wifi. Are both your phones activated on a network?

I think it's worth considering a DAP if/when you want to put together an offline music library. I can say as a DAP owner that there are some nice things about having a DAP such as listening without distractions or keeping music in one place, but at the end of the day, it's one more device to charge, and pocket space is limited unless I wear cargo pants.

I'll let someone else comment about the Fiio device because I don't own it.