So I've put in what I'm using at the moment, but it has been hacked to pieces with me trying every possible random combination of flags I can find.
#######################################
# Board settings
#######################################
CONFIG_SOC_SERIES_NRF52X=y
CONFIG_SOC_NRF52810_QFAA=y

# use devicetree entries to control partitions
CONFIG_USE_DT_CODE_PARTITION=y

CONFIG_BOOT_BANNER=n

# ~2.93% RAM increase if enabled
CONFIG_ARM_MPU=y
# ~2.67% RAM increase if enabled
CONFIG_HW_STACK_PROTECTION=y

# support for serial drivers in Zephyr (mainly for uart)
CONFIG_SERIAL=n

# Low Frequency (LF) Clock Configuration
CONFIG_CLOCK_CONTROL=y
CONFIG_CLOCK_CONTROL_NRF=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_50PPM=y
CONFIG_SYS_CLOCK_TICKS_PER_SEC=1000
#######################################
#######################################

CONFIG_GPIO=y

#######################################
# Onboard ws2812b (disabled while ble issues are being investigated)
#######################################
# CONFIG_SPI=y
# CONFIG_LED_STRIP=y
# CONFIG_WS2812_STRIP=y
# CONFIG_WS2812_STRIP_SPI=y



#######################################
# Bluetooth
#######################################
CONFIG_BT=y
CONFIG_BT_PERIPHERAL=y
 # use nordic company id (for testing - easy to identify)
CONFIG_BT_COMPANY_ID=0x0059
#######################################
#######################################

CONFIG_PM=n
CONFIG_PM_DEVICE=n

CONFIG_BT_DEVICE_NAME="nRF52xx"
CONFIG_BT_CTLR=y
# ~6.53% Flash increase, ~6.66 RAM increase if enabled
CONFIG_BT_EXT_ADV=n

######################################
# logging & debug
######################################
CONFIG_DEBUG=y
CONFIG_ASSERT=n
CONFIG_LOG=y
CONFIG_LOG_DEFAULT_LEVEL=4 #almost guaranteed a segfault when set to level 4

CONFIG_LOG_MODE_IMMEDIATE=n
CONFIG_PRINTK=y
CONFIG_CONSOLE=y
CONFIG_LOG_PRINTK=y
CONFIG_USE_SEGGER_RTT=y
CONFIG_RTT_CONSOLE=y
######################################
######################################

######################################
# memory usage reduction/restrictions
######################################
CONFIG_STACK_USAGE=y
CONFIG_SIZE_OPTIMIZATIONS=y
CONFIG_NO_OPTIMIZATIONS=n

######################################
# These aren't correct - they allow for debug
# messages to flow, but the sizes are almost certainly a problem
# Basically - these are wrong. Ignore them. BLE fails with _and_ without these
#
CONFIG_LOG_BUFFER_SIZE=1792

CONFIG_MAIN_STACK_SIZE=1024
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=1024
CONFIG_BT_RX_STACK_SIZE=1024
CONFIG_ISR_STACK_SIZE=1024
CONFIG_IDLE_STACK_SIZE=512