Roadtrip west-coast USA

Hey I’m planning a three week roadtrip starting from either San Fransico or Los Angeles.

Now is this my first time planning a road trip and wondering if the following distances are possible and enjoyable Within the given time?

I was hoping to visit the following within the three weeks:

Los Angeles

Las Vegas

San fransisco

Seatle

Returning to starting point either SF or LA.

We would like to primarily visit national parks since we have the national park pass. Spending about 2 days in a city max.

Also we don’t mind spending 4 to 8 hours in a car a day if needed.

Ofcourse places like Zion, Grand Canyon, Yosemite will be a must visit. And I’ve seen some amazing sights near seatle that’s why I would like to drive all the way up there.

Any recommendations or tips are welcome!