Online store in Wa state. No physical store.
Do I only need to charge sales tax for Wa state?
Do I need to charge city, county, state taxes if someone buys a taxable product in Wa State or can I charge a flat rate of 8.4% since that is my sales tax rate where I am shipping from?

If I am shipping to other countries, do I have to charge taxes for them? How do I figure out what to charge and where do I remit the taxes too?