As it turns out, there are many interpretations of what comes under the Band of Yokai.
I am still trying to assimilate much of the information from the first article I researched and may have to reread several times, after all this encompasses many hundreds of years of folklore and research.
Yokai, Yurei, Bakemono, Mononoke, Oni…. the list goes on and different writers seem to have different ideas about what relates to what. Bakemono seems to be widely known as something that changes form, some say they stay in certain places and choose victims randomly who enter their domain. Yurei however, are very different according to some sources, they are those that attach themselves to the life of a single target, relentlessly hunting them down and dogging their every step.
Monster? Ghost? Demon? Spirit? seems like Yokai might just encompass them all, but then i could be wrong on that.
More research is needed.