If you buy a new vehicle, and have the license for California, then you will not need to smog it.
I bought a 2007 Ford Edge and normally it is not smogged for 4 years. I had it in Oregon and lived here at the time. When I moved to California, it was about 2 years old, and I had to find a smog station that took my style of vehicle, that the new smog equipment plugs into the OPDII port and controls the throttle electronically during the test. It passed with only 6 PPM hydrocarbons, the limit was 100 or something.
So if the vehicle is brand new, probably will not need to smog it at all. If used, then when you get to California, you will need to smog it. However the need to bring it up to 'standards' like my 85 RV took, that is no longer required, as all 50 states meet the CA requirements today.
If you are attempting to avoid state sales tax, well California will collect the county sales tax rate for the county that you own property in, or live in, unless you bought the RV over 18 months earlier, and are bringing it into the State of California for the very first time. They also ask questions that might be difficult to answer, like have you been employed in California, and what day did you start working in CA. Do you own any property in CA, when did you buy it? If you have been a resident for all this time, they will not allow you to avoid paying sales tax, unless you might be buying this from a relative, or got it in a will.
Good luck!
Fred.