Does closing iPhone apps increase of decreased battery?

Some people say if you close the apps you're saving battery

Some say if you leave them open you're saving them because they stop working in the background and don't need to load again when you go back in?

Which one is correct and proven?

You can stop push or fetch( I can't remember) notifications from apps and emails and that will reduce battery use. It's in the settings

Yes it does it holds less storage

Dnsj