@mtiutiu well my humble opinion is the step-up converter with a lithium cell is a waste of energy and battery life.
Basically at 2.4v lithium cell battery is nearly dead, and at 2V you can't get anything from it. With updated bootloader atmega can easily run down to 2V. So can NRF24 (1.9V) and si7021.
With increased voltage, these components will also naturally increase their current consumption, so in addition to a bit of waste from the converter you have more waste because of the increased voltage.
For AA / AAA the boost converter makes sense, for lithium cells it's just a burden and a hit on the battery life I think.
Just realized I posted on the wrong subject, my message was intended at the CR2032 sensor, which has a hefty reserve capacitor already so should run for a veeeeeery long time without the booster.