Not sure why you would not take 80 west to 29 Vallejo to 37 to 101 north instead of traveling to Williams over.
I work in Vacaville sometimes and travel this route. Many big rigs, RVers travel this route. Just know there are no rest areas.
To answer your question, Williams to 101 approx 100 miles and just over 2 hours travel. Again, many big rigs, RVers travel this route too. And no rest areas.
Both routes have areas you may safely pull over.
We have taken our 30 ft TT over both several times.
Happy Trails
West Beachhouse