may I suggest you start small? (my apologies if you already have done that.)
setup the build environment (Arduino, PlatformIO, UIFlow, ...)
get familiar with your M5Core device
build, download and run some simple examples (blinking an LED, put some text on screen, ...)
now try to setup one watering/soil moisture unit using the provided example
only if that all works try to setup multiple of them
BTW: the watering/soil moisture unit does not use I2C to communicate therefore the discussion in this thread is probably not really helpful for your situation.