I've tried to do some research but I am utterly confused. I am reselling products on Shopify that are primarily fulfilled and shipped out of China. Do I need to collect sales tax in states other than where I'm domiciled? (do I even need to do that?) I'm excited about my new store and want to make sure I'm going about this correctly... I know I should also ask my accountant but I'm hoping someone in this forum has been there - done that and can share.
You collect sales tax for any state that you have a nexus in. All that means is where your business (or store if you are selling in more than one state) is located, sales made to customers located in your state in other words.
With that said, you need to contact the sales tax office of your state and insure that there is not an agreement between your state and some other state to collect sales taxes. That is usually something restricted to the NE state area in my experience.
Always get what amounts to legal information from the source, not the public. Contact the sales tax office, the state web site for sales tax probably has that information too, but call if in doubt.