You can buy products from anywhere in the world to sell on Amazon. Just ask the supplier if they can provide you with DDP (Delivery Duty Paid) service.
PL means your own brand with your own branding on it. If you want to do this in USA, you'll need a trademark for brand registry, so that your listing don't get hi-jacked.
Me-too means Wholesale. If you plan to go on branded listing, you'll need an LLC to get approved by the brand to sell it's product. If you plan to mee too with generic listing, than you don't need an LLC.
You need around $15000 to start PL and $5000 to start Wholesale
You can contact me for more details on the topic.