Friendlyelec nanopi neo full upgrade

I have nanopi neo, it has eMMC chip on board. By default it has own u-boot and operating system. Is it possible to flash eMMC with only stuff required to run openwrt - approrpiate u-boot, and the openwrt kernel? I can't find much information on their website. I am using compiled image cloned from the openwrt repository, it seems to have u-boot stuff in, but I am not sure if it is being compiled and if it is compatible/complete. Can not open or mount output image in the bin/target location to see what is inside.

I write generated .img file onto the uSD-card, and u-boot starts from eMMC and then loads kernel from the uSD-card.

The related problem, I faced issue with fw_setenv in this my build of openwrt requiring some additional configuration (I suspect because u-boot originates on the eMMC) - that's why I am asking if it is possible to have both openwrt and u-boot preconfigured to be flashed into the eMMC working together.