Honestly, Google algorithm has been figuring out ways to rank lower websites that use intrusive pop-up methods on mobile devices, so perhaps having pop-ups for mobile devices isn't a great idea … for desktop it's fine since there is space, but for mobile devices, it's actually quite annoying since people just want to find information fast on their small devices, plus it tends to slow down mobile devices as well.
I use OptinMonster, since their paid feature includes simplified mobile pop-ups
I use OptinMonster, since their paid feature includes simplified mobile pop-ups