I agree with @randybrown that it is too easy to fall down the rabbit hole. :-)
I bought my Sylphyo before the upgrade was available and invested hours looking for the "perfect" flute sound for my iPhone.
I ended up using BS-16i on my iPhone. It is definitely an excellent lightweight solution. It works out of the box with the Sylphyo, is easy to use and has very low latency. Though the BS-16i came with hundreds of instrument presets built in, I generally use the Ixox flute sound font as this sounds very close to my own flute.
The great thing with the Sylphyo is that there is no limit to the different ways that you can go.