Pier and post is okay, but I prefer to use a footing and foundation wall. It's hard to beat concrete in an area like ours that gets and stays so wet. Your best bet for the code issue is to take a walk down to Port Orchard and ask the permit reviewers directly. They will spend lots of time with you and explain your options.
For me, the deciding factor is that I don't want some contractor coming along in 5, 10, 20, 50, 90 years and saying what a hack he thinks I was, rather, I want him to look at it and think "wow, this guy really knew his stuff!"
It's all about quality. Our trade is one where the work we do tends to outlive us. I want the work I do to be in as good shape in 100 years as the day I close out the project. That always starts with a solid foundation.