You can definitely do music recording on an iPad with WIRED headphones - I have an iPad Pro 10.5 that I'll use in conjunction with a 37-key midi keyboard and it's great for travel.
But there is NO world where you are doing realtime playback/recording even with very loose quantization with an iPad and BT headphones. Maybe some day, but that day is not now.
Latency
- under 30ms = acceptable
- between 30-50ms = irritating but you can work around it
- between 50-100ms = easily detectable when you press a key and almost unusable
- above 100ms = patently absurd
And this is latency figures for laying down melodies. Latency needs to be even tighter when laying down drums.
The only decent wireless headphones I've ever used in a recording setting were AIAIAI TMA-2 Wireless+ [1] which uses a dedicated radio transmitter.