How does Ravenous + Titanic Hydra work together?

Greetings,

So I kind of play this game under the general impression of "don't stack unique tags together", without fully understanding the mechanic, and it's not clearly explained anywhere in the game itself. I noticed under Kled's recommended items, they had Titanic as essential, and Ravenous under offensive.

First question: "Passive" and "Unique Passive/Active" You can then have n Passives can stack additively upon themselves if you buy n of the same item? Certain items have a "Unique Passive", like the Spectre's Cowl. This means, when you buy another Spectre's Cowl, this specific passive won't stack again (so maximum of one). However, if you buy another item that has its own "Unique passive", that will work, because the unique passive corresponds to its respective item.

Second question: Ravenous and Titanic hydras together So the Tiamat, which builds into both of them, has a Unique passive: Cleave, and Unique active: Crescent. Depending which item you build, Cleave and Crescent takes on different identities --> If you build Ravenous Hydra, it keeps the Tiamat, and if you go Titanic Hydra, it takes on something else. I tried in "practice mode" building both. If you build Titanic (cone attacks) first, then Ravenous (circle attacks), your auto-attacks appear as if they take on the role of the Ravenous Hydra (circle attacks). If you build Ravenous first, then Titanic, they keep the ravenous hydra (circle attacks). You can choose whichever active you want, but using one active puts the other one on cooldown. (I guess since they share the same name).

So what's really going on here? Is building both a Titanic and Ravenous pointless? Is it worth having both for the stats (for a champ like Kled). The actives overlap, so this is not optimal. Which unique passive does it end up taking on?

Thanks for the clarification.