Open Design > Template. Click Customize Look. The Top Banner section contains the Form Card style options. Corner rounding (Default / Sharp / Soft / Round) controls the border radius on the form card and buttons. The Form Card preset (Shadow / Bordered / Flat / Glass) affects how the card sits against the page background.
The layout and spacing of page sections (hero, FAQs, social proof) is largely controlled by the template and the section background colours in Customize Look > Page Sections. Each section can have its own background colour set independently.
The Navigation section in Customize Look controls the top bar style (Default / Bordered / Transparent / Filled) and its background colour. The Top Banner section sets the page banner background colour, background style (Wave / Diagonal / Gradient / Minimal), and banner layout (Centered / Compact / Banner).