Board Thread:Naruto Discussions/@comment-32617252-20180630010918/@comment-1512913-20180630094929

But of only already existing individuals who produced it, the Tailed Beasts have their own personalities, thoughts, feelings, memories etc. not that of the Ten-Tails. Also we have seen them sleep, bleed, produce saliva and show other characteristics of living creatures... not very chakra-ish.

So I would say, for all intends and purposes, they are physical creatures, but they can take on non-physical chakra state any time or so.