Demetrios1453
Legend
Those all sound fairly low CR creatures which would be perfect. I didn't notice those on the monster list that I saw for Volo and this is a big plus to go with Volo.
Regarding the "flavor and fluff", is it tied to the Forgotten Realms, much? I dislike the Forgotten Realms and when I learned that Volo's Guide was based on it that's actually what prompted me to look at other supplements and led to me discovering Tomb of Beasts.
Very little. The beholder section details a beholder-run thieves guild in Waterdeep, but adapting that to another setting is as simple as changing the city name. There's basically the same issue with name checking the ancient giant kingdom of Ostoria; again a simple name change is all that would be necessary. The section on yuan-ti references some FR deities, but gives a sidebar on how to substitute other settings' deities.
Conversely, the froghemoth and vegepygmy sections reference the Greyhawk adventure "Expedition to the Barrier Peaks", and the mind flayer and neogi sections reference Spelljammer.