Question on withholding tax

Hi all.
sorry if my question is dumb, I could finally set up a NISA account, but I am confused on the withholding tax related to US ETFs.
If I get some dividends paid are they taxed even if it's in NISA? I'm reading that some are and some don't but I still find Rakuten securities website quite confusing so I am not sure.
I thought that everything imvested in NISA is free from capital gains tax.
what am I missing?
thank you

by Affectionate_Cow3076