We have used Popup Domination in the past. Had no issue at all with SERP ranking. There was a few minor issues in the code (nothing major we are just picky) that we needed to address to increase website performance. But overall, love the Popup Domination plugin is amazing. It helped increase our email subscribers.
Haven't used WpLeadMagnet before. I wonder if the 'content blocker' feature on WpLeadMagnet hurts SEO.