Hey there.
Interesting about the RDSP. In terms of the tax implications of the RDSP, I'm not an expert by any means. This is a rare account on my end, as I've only known maybe a few people who have them. An accountant is going to provide you WAY more accurate and knowledgeable information than I would in that department.
On the taxes however, you'll pay no tax on dividends in your TFSA on Canadian stocks. You WILL pay them on U.S. dividends (IRS Withholding tax) if you decide to own them later on inside that account. This is why U.S. dividend stocks are best kept in an RRSP, where the IRS deems it a retirement account and waives foreign dividend tax. Withholding tax will be applied once you open up that taxable account too.
If you were to hold Canadian stocks that pay dividends inside of a non-registered (taxable) account, because dividends are paid with after tax income by a corporation, the government provides a dividend tax credit to investors that essentially makes it as if the dividend was taxed on the corporations pre-tax income. This is a process that depends on the governments level of "gross up" and your overall income level.
Overall, we're not tax experts here and we urge everyone who asks to seek out proper tax advice. We can guide, but we definitely aren't the know-alls of taxes, especially with unique accounts.
But one thing I can say, is don't let tax situations hold you back from owning international equities. In my opinion, having exposure to the U.S. and worldwide markets is key to a well diversified portfolio.