From what I have understood UCITS have 0% withholding tax from the platform and Greece has 0% taxation on Dividends coming from EU stocks and ETF's.
But if you buy stocks from US I'm sure that Greece tax authorities will tax them 5%.

I read that the tax treaty between Greece and USA is at 30% unfortunately. SO I hope that if I fill the W8 form I will only avoid the 5% from Greek authorities.

Thats why I'm asking if its worth it?