海外所得課稅問題

如果我開了線上美股scotttrade的證券&期貨交易帳戶
那麼如果買賣美股若有獲利
台灣、美國都要繳稅嗎?
另外如果買賣選擇權若有獲利
台灣、美國都要繳稅嗎?

如果都要繳稅,那我是否到香港、新加坡或開曼群島等地設立spv就可以合法的不用...
Update: dear Gary:

thank u for replying to my question.
what's the tax rate of capital gain for stock and option in the us?
i'm not a green card holder nor a citizenship owner.will i have a different tax rate?(better than native citizen?)
Update 2: dear Gary:

p.s.:i live in taiwan.so i'm gonna open an international acct. in a online broker named "scottrade" through "w-8ben" form.
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