Well, The Witcher 3 has more optional threads than previous installments. Still, if you just want to finish the game some events are obligatory. The main path is a mix of all mentioned. We have romantic dramas, politics, fantasy, realism, chicks (we also have Richards to rhyme) and the world itself (no Mary Sue, though). It's more like TW1 - you finish an act, to begin something new, with new themes. But without acts structure, everything is (almost) open.
However there are these optional quests (or quest chains). If you liked something from the main menu (he he), you just pick optional quests about it and continue the story.
According to your preferences, you gonna like some Skelligean and Novigradian płots. We'll see.