<p>Currently, pure CAD questions are out of scope of our Stack, but we have quite some cases that edge, where the question about the CAD is about how to make a model printable or design principles or such.</p>
<p>Where do we draw the line in the sand? <a href="https://3dprinting.meta.stackexchange.com/questions/204/the-fine-line-between-3d-and-cad">This was once discussed in 2016, but no conclusive answer defined.</a></p>

I struggled with the same question since I saw the edit, good that you brought this to Meta! Thanks!
As the community of regular and active members is limited, I think it is okay to welcome people in a comment or an answer. It would be a shame to scare people away after their first question, resulting in abandoned questions and unaccepted answers. But, we do need to conform to the Q&A format and sometimes need to remind people this isn't a forum of threaded messages and we do have some rules to participate. We have created some
standard comments
that welcome and thank new members but at the same time lead them to the rules of the site.
It might be a good idea to approach first time (SE) members friendly. Welcoming comments can and tend to be deleted after a while when users aren't new anymore (everybody can raise a flag on a comment to vote for
”It's no longer needed"
). So option 4 would be my preferred option.
Personally I think this site is more welcoming than larger sites as SO for instance. My first experiences at SO didn't make me feel welcome.