How does this compare to Monero and Zcash, and has anyone done a proper comparison or review?
I'm not aware of any detailed comparison. The technologies are different. Regarding use options, perhaps the main difference is that Blackbytes can be sent as textcoins, without any trace on the ledger at all, like cash. Blackbyte textcoins are sent as files over any digital medium (such as email, whatsapp, etc), see details here https://blog.obyte.org/private-textcoins-6a2288d80757.