Sharing a room with a partner vs a stranger
With a partner, you may already know each other’s habits, but a small room can still magnify sleep, work, money, and alone-time needs. Do not assume intimacy makes those issues self-solving.
With a stranger, more explicit rules are needed at the start: visitors, changing clothes, calls, food, cleaning, and property. The advantage is that you may establish fair norms before habits harden.
In either case, protect separate time, storage, and an easy way to say no. Discuss what happens if one person moves out or the relationship changes. Shared rent is a financial agreement as well as a personal one.
Compatibility comes from clear expectations, not from how long you have known each other.