I tend to steer toward the hardwoods like Cocobolo or Bocote. I don't really like the flavor of wood in my vapor.... which is a little funny when you consider how many wood stems and vapes I own. But the the majority of the stems I have... have condensers in them. So the wood flavor doesn't really come through except for on the lips. And that's minimal.
All my stems come with Ti hot ends and fully lined with SS.
There is a reason why wood imparts a flavour and we have no idea of the chemical makeup in the wood oils causing it.
Personally I'm not willing to put anyone at risk with an unknown substance.