Hey, some people publish only their least selling projects on Elements, while keeping best sellers on Videohive. My personal opinion is that the more of your projects you can have at the more marketplaces and visible to more customers - the better. After all, elements earns more than videohive. Unless you’re an elite author (who gets 70% from sale price), and your items have hundreds of sales, and still are generating sales consistently to this day, then yes maybe money wise keeping them only on videohive makes sense. But then again you have no idea how much money these projects would make on elements and how much it at all, would publsihing such projects to elements impact your videohive performance.
After all some customers would rather buy one project once for 14 dollars, than pay much more for a subscription, which maybe they don’t even need.
As for if sales decrease after you put your projects to elements… Maybe, but it’s hard to tell, unless you’re a wizard and can for sure predict what would happen if this or that. Else sometimes projects die on their own on videohive, without elements. Other times, both videohive and elements earn a lot money for a project. And other times the projects don’t sell on neither of the marketplaces
So up to you what to do.