I think the overall idea is let the kid dictate how and if you meet the SO or the parents. As I said earlier, with my D, her OOS bf (both attended college OOS), we just invited him if we went to lunch while visiting. After it was clear they were a real couple, and because he lives a fair distance from us, we let him stay the night here, with her, when he visited.
Just do what you are comfortable doing. Ask your kid what makes him or her comfortable. There are no rules.