Redbubble

So I was about to make an account on Redbubble to sell stuff, but I have 2 questions I'm not sure I can answer even after researching :

• How does copyright even work in there? There are thousands and thousands of products for popular popculture names floating around still selling, and even some religious ones (which I have nothing against, but that are said to be against RB's rules)

• Can you know how much a product sells? I thought I could base myself on the number of reviews first, but then I noticed that the reviews might be for a TYPE of product (like "shirt") and not the specific product on the seller's page. Might be wrong. Not sure if you can see the number of sales anyway.

• I noticed there were some fishy stuff like those being told about the site https://www.reddit.com/r/Scams/comments/3nloy2/redbubble_online_store_is_a_scam/

So I'm considering options. Is there any way to know which one out of the popular selling sites (Amazon, Etsy, etc etc) gives you the most money for the same selling price?