On a general note, so far the cases I've read about are often when their story deviates even a bit from their stated purpose of stay. So if you say vacation, you better show hotel reservations from start to finish dates, return ticket and all. If prompted to share itinerary, but you were also planning on attending some meetup or conference here, visiting an uncle there, maybe going to Mexico or Canada and then back, that's where it gets murky and they could get you.

I read about a case once of someone tricked into answering a work e-mail, for their employer located in their home country while in the US for vacation, and for that they denied entry to this person. Honestly I'm not sure what I'd say in this case.

It seems that points of entry used by the typical traveler that enters through them, are better as they are more familiar with the local situation. If you are the odd one there, you might get singled out as they try to make sense of your story. So I'd prefer entering through an international airport close to where I'm going, than say, by car from Mexico. For now, I'd avoid entering through the south by car, but I don't think the same applies up north.

For your case specifically, threeseed already shared good guidance. Make your trip make sense to outer observants, don't offer them unnecessary avenues of questioning, and keep documentation and contact numbers at hand.