I think the answer may vary greatly from person to person.
But for me, it doesn’t feel like an important/significant part of my life if I’m not thinking about it. I am fortunate to have a pretty functional family - two parents (who I am incredibly close with) and a brother - we all get along well and support each other. I had a fairly normal upper-middle class upbringing and I was raised understanding that I was adopted from when I was young. My family is my family. I have never had the urge to find out anything about my biological family.
When I do focus on it, I sometimes wonder if my (at times, severe) depression and anxiety are somehow related to my being adopted. In a lifespan development class I took for nursing school, I remember learning that “there’s really no such thing as spoiling a baby” because love and affection help mold that child and their sense of safety in the world - it’s one of their fundamental needs. I can’t help but wonder if I received that in my first year of life and whether or not it affects my mental health now.
More than anything, though, the impact is that I just feel so grateful and lucky to have ended up with a family who has shown me nothing but unconditional love.