Having it on will sorta freeze apps to storage that aren't currently in use but are running. Where having it off means apps have to keep opening from the start if the phone closes them. To explain a little better.
Ram plus: Open WhatsApp, app loads from the start, go do other things, WhatsApp is placed into storage to save ram. Open WhatsApp again, it continues where you left off without needing to load.
Ram plus off: Open whatsapp, app loads from the start. Go do other things, phone closes whatsapp to free ram. Open WhatsApp again, app loads from the start.
When working as intended, it shouldballow you to keep more apps open and prevent apps loading from the start each time. Should save battery and reduce heat. Though from what some of you have said, sometimes the opposite happens. Guessing it's dependant on how you use your phone. It also only really gets used if you fill your phone's ram with apps