How to Customize Google Forms
Why a guide to styling a third-party product is not reproduced here, and where the styling options for your own forms are documented.
The page this one replaces walks through what Google Forms lets you change about a form's appearance, what it does not, and then makes the case for switching.
Tinyform does not document other products, so there is no counterpart. What you can change about your own form's look is covered in two places: /help/customize-your-form for the theme, fonts, colours, cover and logo that the Customize panel offers, and /help/add-custom-styles for a stylesheet of your own on a published form.