Soundquality bluetooth headphone

Hi guys.
I hope to get some info here.
I want to connect a B&W P7 Wireless headphone via onboard bluetooth on my rpi4.
This headphone supports aptx.
Can you tell me if the sound will be lossy or lossless?
All my music is stored as flac files.
Hifiberry Dac2 is installed.

Greetings Daniel