There are many places as you get closer to the ocean and some rv parks, and right next to the ocean. If you grab a good map, and your Miata, take a trip to the ocean for the day and drive/scout a couple of the routes when you get to Santa Rosa or Cloverdale- perfectly positioned.
Most of the places are generally in my mind as I haven't really been rving for a long time, but motorcycled many of the roads quite a bit, but really pretty easy to locate.
Also excellent motorcycle roads. Great opportunity to rent a bike if you are a rider...except for the rain conditions.
The question I don't know is how well your rig would do on highway one because of the tight turns and possible rain slide construction..but it may be a good length...just guessing, but width can be an issue...maybe a bigger issue where there is construction or temporary cement guard rails.
The software service might be ok for the route, if you want to take the rig to highway1, but not for the construction?, as rain sometimes causes slides in the sides opposite the ocean. But it is such pretty country, you can't go wrong with scouting for one day, stopping at the ocean for sea food, and then moving the rig the next day, which is how I would do it in case the gps is not on top of the construction activities if there was a slide overnight in this rain and you are not sure about handling the hair pin curves along the ocean if you go for it.
Frankly, I live south in Vallejo and you can cover a lot of ground in the Miata without taking the rv into the ocean areas and worry about salt issues, traffic, and highway 1. And you can also rent a place near the ocean for the night pretty easily this time of year as well.
During this time of year, the traffic should not be bad at all, but mornings and evenings are still best.
Send me a pm if you have concerns or run into a problem. Would be happy to help out in my neck of the woods. Should get back to you in less than 24 hours generally, maybe within a few hours.