I'm not familiar with these websites. What should I know about them? Did you already write about your experience?
1688.com is Chinese B2B marketplace, but really it's B2anybody since most places have no or very low MOQ.
If you are not in China you really need to use an agent to buy for you (same agents that buy from Taobao can usually do from 1688), Superbuy is who I use currently, but other agents I use are Spreenow and CSSBuy.
An agent purchases the goods for you and have them sent to their warehouse, then on-ship them to you. You pay first for the goods and domestic shipping, and then for international shipping once it's at the warehouse and ready to send to you. Most agents also charge some service fee as a percentage of the product and domestic shipping amount.
Superbuy, Spreenow and CSSBuy all accept Paypal for payment.
Good places for learning about Taobao/1688 and agents are...
reddit /r/taobao
reddit /r/fashionreps (people who buy knock-off fashion stuff do a lot of taobao buying)
4chan cgl (people who but cosplay stuff also do a lot of taobao buying)