The likely answer is to do with audience biases. A survey conducted by an email marketing provider is almost certainly going to have different results to one conducted by PPC management tool, as their audiences have different skillsets and biases, skewing the results of their sample. As such, we should take the specific ranking of different strategies in these studies with a pinch of salt.
Beyond that, avoid using all caps, too many exclamation marks, and hyperbolic phrases ("ACT NOW BEFORE TIME RUNS OUT!!!!"). Poorly formatted HTML in your emails can also hurt how they’re handled. Every spam filter is different, so an email might pass through one filter but get flagged by another. For more comprehensive info on how spam filters work and how to avoid them, check out this guide by MailChimp.
CTR is the number of clicks on your CTA button, versus the total visitors to that landing page or ad. If 1000 people visit your landing page/view your ad, and 650 people click on the CTA, your CTR is 65%. A high CTR depends on a number of factors, chief among which are the value proposition on your page/ad, your CTA’s placement, and the relevance of your content vis-à-vis your target audience.
If links and looks are set, begin interacting with the page. Abandon it, adjust the window size, convert. Are error messages appearing when they’re supposed to (if, for example, you don’t input all the form’s required info)? Is your CTA button working? If you abandon the page, are you retargeted with ads? When you resize the window, does your landing page respond accordingly?