Interesting masternode coin, hope to see details of the coin especially total supply, premined amount , etc... Might try to setup one masternode with my Ubuntu vps.
BTW, what is "IP/Onion"? What is the Onion for?
I'll just answer your question. The IP/Onion field is meant for all kinds of addresses.
I guess that this coin by default will have Tor integrated into the wallet, so the wallet will run befault on Tor network.
It makes you a little bit hard to trace, because blocks are synced via tor network (takes a little more time usually, because the tor nodes can be quite slow at times), which means that all of your transactions are broadcasted via tor network as well, which encrypts the data you send through it and "peels" the encrypted data layer by layer (like an onion yes), which means that it will be fully encrypted at the end server. This is why the network is pretty secure.
You can use the picture below as some kind of lesson, which is pretty simple looking:
I personally see Tor and anonymity networks, as a way to protect our freedom of speech and identity. However some sick bastards misuse it, so there is a negative side as well.