Re: Keep or close all apps in the background?
If you have a lot of apps "open" and some of those apps are syncing in the background, your phone, no matter how much ram, will be slow to address your request. Only sync the apps you MUST have. FB messenger is a huge resource hog.
You can clear open apps all you wish. The only downside is that the phone has to open the app again....basically starting over...losing where you were at...such as you were on page 11 and clearing the app will start you back at page 1.
They say to let android manage the apps. That's fine if your multitasking between apps all the time. There's no problem with that as android does a good job at shuffling resources. But clearing apps, does in fact, make your phone run smoother but only until you start opening apps again. With that said, B. Diddy has steered you in the right direction by saying let android manage them.
Your home screen redraw is most likely from an app your using. If the game (or app) your playing/using is using Open GL for it's graphics, your home screen might redraw here and there as it has to switch graphics drivers. It happens on all phones. Even the iPhone....I know cause I have one. But most likely it's FB. FB loves to take over your phone.