Do not sacrifice UX for SEO. Good SEO is good UX.
Knowledge usually derives from past experience. Many past SEO tactics and strategies are obsolete and counter-productive knowadays. Be careful your agency isn't pulling the wool over your eyes or obfuscating -- the only SEO is SEO that brings quality inbound traffic to your website. The only CRO that is effective is CRO which increases your conversions. Both SEO as well as CRO should not be seen as independent of the User Experience. They are part of it.