For the firmware, I would have stuck with Micropython if it weren't for its lack of dual core support (required in my case for simultaneous BT + fast sampling A

For the firmware, I would have stuck with Micropython if it weren't for its lack of dual core support (required in my case for simultaneous BT + fast sampling ADC). About efficiency - ESP chugs gobs of power, comparatively (something like 50mA average, and that's with all the relevant power saving features enabled). By comparison, an nRF or an STM32W0 is single digit mA.