Am i right in saying the best CPM is from people searching keywords in Google then landing on your site compared to paid traffic landing on your site (ie Facebook ads, PPC etc) Does that make sense?
Yes, that is generally the case. If coming from Google search, then there is much more intent as they were searching for that. Coming from social media, then generally that just come across the advert with less intent.
I have had some success with Google. In Adsense at first, now I use Video and search ads to scale bigger.