Most camellias will eventually reach small tree size if left unpruned. They grow pretty slowly, though, and respond well to pruning, so once the plant gets to the desired height, you should be able to chop it back every year or so to keep it the right height.

I haven't heard that 'Cotton Candy' is smaller or larger than other sasanquas, but someone who has grown it may be able to chime in with that info.

a couple that i grow which tend to grow wider than tall are 'shishi gashira' (fall bloom) and 'chansonette' (spring bloom). neither has grown over 5' tall and 'chansonette' is barely 3.5' tall. for what it's worth, you will see them both listed as either c. sasanqua or c. x hiemalis,depending on the source. american camellia society lists both as c. x hiemalis, a hybrid of c. japonica and c. sasanqua.
here is a pic of 'chansonette'.
{{gwi:368430}}

That's a nice photo of 'Chansonette'- I agree that 'Kanjiro' and 'Chansonette' are good candidates for a smaller sasanqua. I'm really not familiar with 'Cotton Candy', but any sasanqua could be pruned for size.

Bob Green of Alabama has been breeding a number of sasanqua-type camellias, and most are bred to be fairly compact. I'm not sure how readily available those varieties would be in California, though?

Here is a link that might be useful: Sasanquas at Green Nurseries