Yes, you can switch templates and choose other template pages while creating your website.
Please note that changing your website template will also change your header component. This is because you can only have one header per website. If your navigation is in the header, you will need to recreate it in your new template.
If your pages are already published when you are changing your template, your new header will appear on in your content editor, but not on your live pages until you have published your changes.
Learn how to find the website templates and choose the best option for your project here.