Welcome.
I'm almost fifty. I have the ability therefore to reflect on my life in retrospect. My parents had two very different personalities. My Mom was more like me since she was laid back and contemplative. My Dad is textbook ADHD (undiagnosed) and the epitome of nervous energy. My Dad is also the kind of person that has very strong opinions and has no qualms about sharing them and no qualms about trying to direct members of his family to do things that he thinks they should do. Throughout my life I've felt that my Dad has pushed me and pressured me to accomplish things that he thought would be good for me. I put up resistance to his pressure from a very early age. Depending on his level of persistence, I would sometimes acquiesce or other times give in, but not without protest.
At my age I have the wisdom to understand and admit that I've accomplished many things that I otherwise wouldn't have accomplished had it not been for him pushing me. My priorities are different that most NTs and while I can be extremely motivated and committed to accomplish things I'm interested in, other things that are necessary for independent living (e.g. jobs, better jobs, loans, mortgages, investing, a strong work ethic, etc) are things I had little motivation for on my own. He pushed me with things like that.
I think "push" is good descriptor for me to use because it connotes an idea of something that's not in motion or something that needs to be prompted in order to be set in motion. Once I was pushed in those directions, I'd often develop enough interest or experience to continue those things on my own.
I'm not ashamed to say that I needed him to push me. I hated it while it was happening and resented it at the time. But I did still accomplish everything I've been able to do through my own efforts; I just didn't have the forethought, interest, idea or motivation to start those things. I still feel like I need mentors in my life and I'm not ashamed of that either. For example, I regard my accountant to be a key part of my life and she is a mentor to me more so than in a typical accountant/client relationship.
I'm also a parent although my children are younger than yours. I can understand your desire to respect your son's adult independence, but not everyone is the same in regard to their ability to be independent. It's simply a fact that some people need more direction, coaxing, pushing, etc. Especially when they're just starting out. You feel reticent to nag, direct or push your son. I get that. But, you know him better than anyone. If you feel he needs to be pushed, I'm sure you can find good ways to do that. For example, you could tell him why you think he should achieve a certain goal in his life and explain your reasoning, the pros and cons for achieving or not achieving the goal. Then you can persist. If he tells you his reasoning for not wanting to achieve that goal and he's adamant about it then at least you two are having a dialogue that you can continue.