Accessibility Visibility Question

Hey all - my apologies if this information is somewhere, but I've done some searching and can't find what I'm looking for.

My team and I have some questions about the accessibility visibility feature. Do text boxes need to be marked as visible, or will a screen reader automatically read the text? 

Additionally, when you have items grouped, do you need each individual item to be accessible to the screen reader, or just the group? For example - let's say I make a custom button with a shape, icon, and text. Do I need all three individual items to be visible, or just the group itself?

Thanks in advance! :)