Ambitious. Have a great trip. I for one have to plan extensively and I'm not the serendipitous type.
Since you are planning in the middle of the summer there will be plenty of rigs on the road and you may not always find a spot easily, especially in Yosemite.
years ago one could show up at the CG gate at 5 AM or so and get any open spot. Its not so easy now.
I've tent camped at Sequoia in years past with no problems. Ruby's at Bryce had plenty of space, and Zion campground was nearly full but we had reservations.
Since you want to 'wing it', I'm sure you will have some small problems but you will have some great stories to tell.