i/o expander

Hi, i'm working with hardware engineer for a project
this project is in the audio/midi fields, some knobs, some led and encoder, bluetooth, buttons, display, audio board etc...
he suggest to wire all the parts on the i2c bus using the PCF8574 I/O Expander and the PCA9698

then i have a couple of questions

1. is simple to program this configuration?

2. may i have latency problem with audio and midi?

3. suggestions/advice/things to avoid?

4. coding suggestion? (library)

You might want to have a look at https://github.com/sumotoy/gpio_expander/blob/master/README.md ? Maybe sumotoy can answer your questions better...

Then, the I2C-library "I2C_t3" is better than "wire".

If it interferes with audio, maybe increasing the audio-interrupt priority can help..

Thanks frankB!