We have probably taken 25 plus, 3K plus road trips. So these are our thoughts
1) Which will you enjoy more? Planning every night, or going where the wind blows you? Nothing wrong with either approach, folks are just different. We are where the wind blows us.
2) Anything you have every read about, like Yellowstone, Mount Rushmore, is you and 50,000 of your best friends. All good stuff to see but they are crowded . Something we don't like.
3) Very often it is the small stuff, that turns out to be the best.
4) campsites are like motels, there is always one somewhere, it maybe 75 miles further than you wanted, but you will find one
5) We are a big fan of KOA's, not because their campgrounds, are all that great.
but because if you have the KOA app, you can decide where you want to go that day, make a res online and have a site without all the worry of "where are we going to stay tonight.
6) Our in-laws, plan every detail, that would drive us crazy. On the other hand our go where the wind blows would drive them crazy. So I think figuring out what makes you happy in that way is a good first step in your planning