ExpressionEngine doesn’t dictate the design or front-end structure of your site. You should be able to design it to be single page and responsive on the front-end without issue as long as the developer understands how EE works.
You can use just about any front-end framework to accomplish your preferred method of employing a single-page site (lazy loading etc.) and then make the page dynamic by converting it to a template, and substituting your static content sections for dynamic ones using custom fields setup in EE.
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