Thank you for asking this, because I’m curious too!
I’m not engaged yet, or even really close to that yet, so I’m afraid I don’t have a very concrete answer for you.
However, I’d say that my bf and I have done a fair amount of discussing important issues. Back in January, we discussed some stuff like how we would handle finances, where we’d like to live someday, and how many kids we want, but it was mostly me bringing that stuff up, and my bf finally admitted that he was a little uncomfortable talking about this stuff when he was unsure of our future. So I left well enough alone, and stopped pestering him with that stuff.
A few months later, he decided it was time to start thinking about the future, so for the past 6 weeks or so, he keeps bringing up a lot of stuff about our career plans, when he sees himself being ready to marry, how old should we be when we try to conceive, will his family be able to accept me (we’re from different countries/races/cultures), how manageable is my bipolar disorder, how will we deal if our children inherit some sort of mental illness…
We only see each other on weekends currently, but each weekend, we sort of set aside some time where we’re free from distractions to just cuddle for awhile and talk about whatever’s on our minds. Like I said, lately he’s been initiating most of these conversations, but I’m glad that he’s ready to talk about it, because my general stance is that some of these things SHOULD be discussed before even getting engaged, in order to avoid problems or disagreements down the road, when things might be more serious.
Because my bf got overwhelmed the first time around, I definitely understand that it can be overwhelming. I guess my advice is to address one topic at a time. Maybe set aside some time to talk once or twice a week; talk about one issue (i.e. kids, or career goals) and then give yourselves a few days to process what the other person has said. Next time you talk, you can either revisit that topic if you have more questions, or else move on to something else.