Put messages on any page talking about your company’s products or pricing, and put lead flows on all the other pages.
Put lead flows and messages together on all pages.
To determine where each should be used, randomly divide the pages of your website into two even groups. Then put messages on all of the pages in one group, and lead flows on all of the pages in the other group.
It doesn’t matter which pages each tool is used on, as long as the tool is customized to match the pages it’s added to.