Answer: Please find the following Software and Hardware advices;
1/ Use <AT+KSLEEP=0> (The sleep mode has to be managed by your application via the DTR)
2/ Use <AT+KSLEEP=1> (The Hilo manages itself the sleep mode)
VBAT: no impact on the consumption.
VBACKUP: If unused, you have to put a capacitor to the GND.
VGPIO: If you use this signal as a power supply or as a input signal in your design, it can impacts the electrical consumption of the Hilo.
POK_IN: The best way is to drive it with an open drain.
SPI -> Not connected?
ADC: If you use it, it can impact the electrical consumption of the Hilo.
GPIO: All the GPIO have to be put in a “passive state” according to your design. If you do not use the GPIO, the best configuration is INPUT with a PULL DOWN.
SIM: The Hilo manages itself this signals and put it in “passive state” as soon as possible. (when no access to the SIM card is requested)
PWM: If you use it, it can impact the electrical consumption of the Hilo.
UART: You can disable your UART in order to have a less consumption.
AUDIO: It strongly depends on your design