I'm not sure what it's like on iOS, but on Android the latency renders attempting anything "serious" impossible. There is a noticeable delay between pressing an on-screen key and getting sound out. I don't even want to imagine what a Bluetooth keybed introduce in the latency chain!

Do iDevices not support hardware (USB) MIDI?

I notice no latency with my USB midi keyboard. And the MicroKey Air I have is also real-time, in Bluetooth. [the Bluetooth headphones on the contrary have a noticeable delay, so prefer the almighty jack 3.5 mm connection]