Does different Headings Size have an impact on SEO?

Hi guys,

New to the entire SEO optimization and was told by my past seniors that any heading is fine and is mainly a sizing for the font? I saw a couple of posts that labels (H1) and (H2) as though there is a key distinction between them.

Currently, my website's article is using only H3 and H4s headers, should I be changing them to H1 and H2s?