in my case, i need to update my gapps, thus when i flashed gapps, i flashed the latest ROM available. and LOS, is the latest ROM for Moto X atm.
from my experience i dont need to flash any experimental build after system format. And i'm always format my system partition when im going to update my CM. And it is the same case when im updating from CM to LOS.Officially, if you're not doing the clean flash after system format, you have to flash first "experimental" build that will migrate all your data and only afterwards you can flash nightlies.
Since we don't have official nightlies yet, there's no "experimental" build. So I suggest to wait and in the meantime run latest CM nightly. Or a clean flash of LineageOS.
#include /* * Your warranty is now void. * * We are not responsible for bricked devices, dead SD cards, * thermonuclear war, or you getting fired because the alarm app failed. Please * do some research if you have any concerns about features included in this ROM * before flashing it! YOU are choosing to make these modifications, and if * you point the finger at us for messing up your device, we will laugh at you. * */