Questions:
1. How does the marriage take place? What are the qualifiers? Is there a new "romance" value? Do you have to give the NPC a Diamond Ring (rarely sold) when you ask them to marry you?
2. What sort of benefits come with being married? New dialog? New items sold by NPCs that sell stuff? Random gifts from time to time? A special "Lover's" buff when you mirror back to, or respawn in the same housing the NPC occupies?
3. What about NPC death? Each NPC spawns in with a different name, so I have to ask. Is that NPC now invincible? If they die, do they respawn with that same name every time? Or if they die and they respawn with a different name, does that mean you are no longer married to that NPC? If that last one, does that mean in order to "divorce" someone, you have to kill them/let them die (dark)?
4. Does this include all NPCs, or are there certain outliers? The Dryad seems pretty indifferent about romance, especially given her age compared to most other Terrarian inhabitants. The Tax Collector, Merchant and Clothier are all old. The Cyborg is a Cyborg. Some NPCs like other NPCs (e.g. the Mechanic likes the Goblin). For the NPCs that have an attachment for others, does that just mean you have to try harder?
5. Tying back to the new dialog I mentioned in #2, will some NPCs develop new personalities? For example, if you marry the Tax Collector, will he stop being such a greedy jerk? If you are able to romance the Dryad, does she warm up to the idea of love for a mortal after a while, despite the centuries-wide age gap?
6. What other interactions open up? Do you kiss like in Stardew Valley? Can you snuggle on the sofa together? Can you go fishing in the nearest pond together, or maybe fly kites with each other on a windy day? Do some NPCs have activity preferences over others if that's the case?