Hello @Alexandre__Promont,
you can find expected current consumption in the datasheet. Generally, the power consumption depends on various conditions such as clock source, clock frequency, if there is some peripheral running, if the GPIOs are in analog or digital mode, if SMPS or LDO is used and so on
You can find some tips or information about low power modes and how to reduce the power consumption in following links:
AN5071 - STM32WB Series microcontrollers ultra-low-power features overview
AN4899 - STM32 microcontroller GPIO hardware settings and low-power consumption
Reference manual for STM32WB55xx
But I am not really sure if I understood you correctly. You were trying the same code on various different boards and every time the consumption was different, right?