Will Cyanogen 13 update to Lineage 14 and preserve apps, data etc?
If you install CyanogenMod 13 then you cannot install lineage OS 14 without wiping the device.
If you install CyanogenMod 14 then you can directly install Linage OS 14 without wiping the device, but it is not guaranteed.
If you install CyanogenMod 13 then you may install Lineage OS 13 without wiping the device, but it is not guaranteed.

Lineage OS web site as more clarification.

http://lineageos.org/Update-and-Build-Prep/