Will 2 installs of WP affects things like SEO

Hi,

I have a site that I want to use 2 different themes for. 1 for the Blog, 1 for all other pages.

I think the only way to do it is to have 2 installs of WP, right?

I was wondering how that would affect things like SEO, etc.

i.e. Say I had the yoast SEO plugin installed, would I need that on both sites?
i.e. Is there a way to sort of link the 2 installs together, so the 1 dashboard controls everything?

Would doing this create a lot of problems?

Any ideas would be appreciated

Thanks