Forgive me the long post please!
First of all - being a bit scared is really normal. One of the things that makes the adoption process so different to having a birth child, is the way you talk about potential issues and problems from the very off. Yes, it is more likely that a child who has been traumatised and in the care system, will have some additional needs or issues, but they really make you consider this from the off, and when you're talking about abstract, theoretical children, it can be really daunting. And even though i don't generally compare adoption and the 'standard' route to having children, but I can't help wondering how many birth parents would have been daunted if it was required before conception to attend workshops which explained in detail how many children have various disabilities and special needs. Whereas in adoption, as part of preparing people, they really do shove you in the deep end and make you think about it straight away, and that's an experience!!
I can speak anecdotally, and say that of the families I know, the biggest group of families by far, are those whose children do have some additional issues - not necessarily diagnosed special needs, but perhaps their kids have insecurities, milder issues with attachment and trust, or they need some extra support in school, or they have some social delay, or act younger than their age, etc, or some combination of that. Or perhaps it is diagnosed special needs. But what these families have in common, is that they are strong families with much happiness! Yes, sometimes they need to parent their children a little differently, or may need to access a bit of support, and so it's not always the same as if they had birth kids. But everyone is used to that, that's life, and there are no serious problems.
And of course there are some families whose children seem to have very few or no issues at all, which is great! So yes it can happen
There are also families who have more serious issues, which means parenting a lot differently and accessing support and going through a lot of struggles. BUT, that doesn't have to be hell, and by thinking about it in the abstract and not seeing these families, is you miss the unconditional love, and fact that they are indeed a family and you don't see the good days or the progress children can make.
There's just no way of guarunteeing or knowing exactly how things will pan out, and it's the uncertainty which is difficult
If I speak for me....I have one child who has some issues based on his past, but for the most part, I don't parent him significantly differenty than I would parent a birth child. And two children, one still at home, who have had much more significant issues. But with all my kids...parenting differently, just becomes the way of life. I love them utterly unconditionally, and I take such pride and joy in their progresses and achievements. Yes, sometimes it's been very very hard, and i can't deny or downplay that, BUT i have never regretted adopting them, because they are my beloved children, I would not be without them for the world, despite the difficult things. And that's what you miss when you talk in the abstract. Also, there are good days and joyfull moments going on all the time, whether big things or little things. I've had a tough, but utterly 100% worth it ride.
I think it's wise to prepare for additional issues. I really don't think it's good to be scared into assuming you're always going to be miserable or regretting it, because that's not the reality for the vast majority of people.