Interstate 5 should be maintained being open at all times even when snowing, versus on other roads even on 101, they do not necessarily maintain the road open if weather gets bad. Like someone posted before, cannot imagine you would avoid an Interstate and take other roads should weather is bad. By the way, 101 is much more winding than I-5. During wet weather, it can be more difficult to drive than I-5. Also it has climbs too, going thru mountainous region.
If you are afraid of driving in snowy condition, then probably you should not take this trip driving, but fly Alaska Airlines up.
If you are afraid to drive in bad weather, and afraid to drive slopes, then I dont see how you can take this trip by driving.
Get a good map from AAA, look at the mountain passes along the way and see their heights then decide if you want to drive.