The homepage and/or contact us page template layout is located in layout can be found in your Design Manager in the Theme Name Blog folder (Templates / Custom / Page / Theme Name). The templates will be named Homepage and Contact Us.
While each default HubSpot them utlizes the same custom modules, their layouts and features may vary from theme to theme. To get a better sense of what the various theme Homepage templates look like, check out the links below:
All of the defaut themes with the exception of the Velocity theme, include a Contact Us page template. The contact us page includes company information and an HTML module to paste Google map module. The Velocity theme uses a standard landing page template.
Modifying custom theme templates
You can clone any template to create a variation that you can customize, while leaving the original template untouched.. By cloning a template, you ensure that you always have a master template that you can refer back to.
You can also always roll back a revision of a template and or page, if your are unhappy with a change that you make.
You can customize your template layouts, using Template Builder in Design Manager.
To learn more about structuring templates, check out this article. In addition to making changes to your templates, you can also add modules directly to particular pages using the content editor on any page created with a template that uses a flexible column.