It is kind of hard to answer all the questions.
First off when you get into California, just south of Eureka you have an option of taking the lost coast vs. 101. DO IT. The road is totally amazing. About 125 km's down semi-paved roads with 18% grades and gravel switchbacks. Not to be missed. It took me over 4 hrs to ride it. A bonus is you come out in the land of the giants, redwood forest.
Plan on the temp's being considerably cooler along the coastal portions than inland. It can be 15c different depending on the weather patterns. The weather itself will change. Around Eureka and northern coastal areas, expect fog in the morning, sometimes most of the day. The same holds true when you ride PCH 1 south of Carmel towards Santa Maria (through Cambria).
Regardless of when you go expect slow moving traffic south of Monterrey, RV's pulling cars, tourists etc. It is a bit better midweek, but still quite slow going.
I planned my route the old fashioned way, using a Rand McNally paper map. That is how I plan all my trips. Hotels were booked ahead of time, so I knew I had something on the other end (went during a busy time), and also knew how far I had to go that day.
Finally I wore armour on the coast, in the valley, through the mountains. I don't ride without it. When hitting the 40c plus temps in the central valley I had basketball shorts under my armour vs. pants - still sweated but not as much. Take plenty of water with you and stay hydrated. Be sure to fill up when you get to 1/2 a tank as some areas the gas stations you see will charge about $2 a gallon more than in the major centres. Oh yeah, don't count on your mobile phone working. You will go through sections with no coverage. I took a SPOT just in case. If you don't have one, happy to sell you mine for half of what I paid.
Hope this helps.
p.s. if you have time, consider the Naciemento - Fergusson Road. Awesome, awesome, awesome. Same with US 33 into Ojai.