Why has the oil separated?
Because there is no palm oil or emulsifier in it. Stir it back through before use.
Is there added sugar or palm oil?
Not in the plain butters, which are nuts and a little salt. Flavoured and chocolate versions differ, so check the jar.
Are they suitable for vegans?
The plain nut butters are. Check individual jars for flavoured versions.
Should I keep it in the fridge?
Not necessary. A cool cupboard is fine and keeps it spreadable.
Which is better, smooth or crunchy?
Entirely preference — the recipe is the same. Crunchy has pieces of nut stirred through.