[Q] Notifications and lit up screen topic

Hi folks!

I have a maybe silly question ... but I found out that some apps with their notification light up the screen for a few seconds, and some apps only vibrate and do not let the screen light up. Also Whatsapp is sometimes lighting up the screen ... sometimes it doesn't! How is this controlled, and how can I control this? I know about the "silence" option, but I would only to let it vibrate and no screen light up...

Thanks!