Where to customize the template

Good afternoon. I am writing because I can’t find the place in WordPress to customize everything (1, 2 or 3 columns, full colours, etc.). Pressing the standard button of WordPress “Customize” it only allows me to customize basic aspects, but not in a deep way. I wonder if the only way is through HTML.
??I remind some place in WordPress where it was possible to customize deeply with no HTML.

?Thank you in advance.