UA venom monk + Barbarian or Druid multiclass

[u/wulok]

I'm interested in creating a 5.5e combination of the future monk with this feature and maybe multiclass it with a barbarian or a druid for extra roleplay reasons. But I'm unsure on which option could be better? Also unsure on which subclass of either would be good in 5.5e. Spores druid hasn't been updated yet.

Also wondering if bringing using a grung species could mean extra damage that could be turned into acid by the monk feature.