Is the outline based on competitors?

No. It is a standard structure. Compare it with the top results yourself.

How many H2s should a post have?

As many as the topic needs. Each should cover one clear point.

No. It uses fixed templates in your browser.

They can differ slightly, but both should match the page topic and intent.

Pick the page type and the tool returns a heading structure. Replace each heading with wording that fits your topic, then write the section.

Always check the current top results to match search intent, then add what they do not cover.