Paid hosting and SEO benefits

Not necessarily. If you have a free subdomain it will rank lower because Google doesn’t like them. However, there are a multitude of factors that come in to SEO ranking and that is beyond the scope of this forum. Someone here might be experienced enough to give you tips, but that’s not me. Otherwise, you can search up websites that specialize in SEO (SEO checkers will not work because of the security system but that can fixed with Cloudflare if you have a custom domain).

Technically, yes. Because your website would be able to handle more traffic and would load faster. That would lead to more visitors, thus increasing your website’s popularity.