Check you are using either aptX HD or LDAC for Bluetooth. Should be in the settings on the phone. You might find this is actually better quality than wired (depends on the quality of the DAC and headphone amp in the S9).
320kps compared to 24/192 should be noticeable IMO.
Update…just googled the S9. Wired should be decent.
‘Samsung continues to support high-resolution audio up to 24bit/192kHz, as well as DSD files, and has gone against the grain by keeping the 3.5mm headphone jack.
That means you can plug in your favourite pair of headphones without the need for an adapter. There’s also a pair of AKG-branded in-ears in the box, but they sit a little on the rich side for our tastes, with slightly boosted bass.
Opt for something more neutral and you’ll get to hear what the S9 is really capable of – a clean, clear and detailed sound, with plenty of drive and a decent amount of nuance and expression.’