Nmelius1210, you got some decidin' to do. And some researching will be needed to make those decisions, especially if neither of you is used to spending 8-10 hours a day driving in the car.
One question you might discuss: Is your destination, San Francisco, more important than the process of getting there?
I agree with those who say there is nothing like being on the ground and driving through the changes in terrain and weather and what you see on the road along the way. By that I mean what is being transported by semis. Not everthing is small enough to go in a container.
But if your primary reason for the trip is seeing San Francisco, then perhaps you should concentrate on that.
My husband and I drive from Tucson to the Seattle area every year in mid to late April. We drive back in late September or early October. We have taken many routes to cover that roughly 1600 miles each way. All are interesting. Yes, we do want to get to our destination, but we love the going -- even on forever roads, those that seem to stretch into infinity.
Another question might be: Do we want to do a slice of America or dig deeply into one kind of place or experience?
An example of a slice would be driving from point A to point B on one route and back to point A by a different route. An example of digging deeply would be concentrating on CA or national parks as others have suggested.
I'm a woman of the west. I spent my first 30 years in Texas. I lived in OR and WA a total of about 25 years. I've lived in AZ for 12 years. Yes, there are wide open spaces and there is lots of spectacular scenery and some incredibly beautiful cities on the left coast. Yes, there are some other cities in UT and TX and NM and AZ that are so culturally different from NY that you will think you are in a different country.
But the roughly 2 years I spent in Cincinatti and the visits I've made to the midwest and southeast and deep south and northeast taught me that there is lots to see and experience no matter where you go or how you get there. My husband and I prefer to drive, but if we don't have time to drive all the way, flying, renting a car and driving is the next best thing.
Fortunately, y'all are getting started young. You don't have to see it all in one trip. Whatever you decide to do, have a great time!