Hi gmrck,
The link below shows a comparison of advertisement current. nRF52840 has by far the lowest current consumption compared to MG24. It may be helpful to you.
The output of the MG24 is designed for 20dBm or higher. On the other hand, the nRF52840 is designed for an output of 8 dBm, which is by far the best choice for small output power.
The nRF52840 automatically sleeps when there are no events by RTOS, but the MG24 BSP does not seem to support this feature yet and consumes current unless it is explicitly put to sleep.