All this is correct, but keep in mind that you still leak domain names until ECH (encrypted client hello) is in wide-spread use. It is of course still a good idea to use encrypted DNS, just don’t assume your ISP can’t see which websites you are accessing.

Can anyone explain to me if a headless chrome browser is dangerous the way a regular chrome browser is?

Almost. You want to make sure to keep it as up-to-date as you would a regular Chrome browser. It does almost everything a regular Chrome does, including running arbitrary scripts on websites.