all builds suffer from minor problems with specific mPCIe combinations. If you run into problems check this test matrix for some known working/not working combinations.
To convert mPCIe to mSATA you have to enable the corresponding patches in u-boot-mvebu. Afterwards rebuild u-boot with our build system and write the new u-boot to your boot medium. If you need assistance ask in the forum.
In case you ever run into troubles and ask for help in the forums please ensure to provide a serial console log (UART adapter on board accessible through Micro USB with 115200/8/N/1 settings)
The boards can boot from various sources that are adjustable with a DIP switch. Comprehensive information about the necessary preparations available here.