Yes, you can board with a vape pen. Apparently, because of the batteries, you actually are not allowed to pack it, so you pretty much must carry it on with you.
THC is a different story and depends on the local laws (not banned in itself any more than nic or non-nic vapes) but if THC is illegal where you are or where you are going, you risk being arrested, whether you pack the THC or carry it on board. This could even include residuals on the vape pen from when you last used it. Standard concerns about pot and its derivatives apply.