Confused about how ETFs work

Sorry a bit of a dumb question I can’t wrap my head around. I’m confused about how they’re taxed or calculated.

Hypothetically if I wanted to withdraw after 5-10 years, will I be taxed on the growth at the marginal income tax rate? And if I have a high income then how much do I even get?

Does this mean I am capped to only withdraw $18,201 a year (with no income in these years) if I don’t want to get taxed?

How do people withdraw large amounts (100k+) yearly without being penalized over 50%?