GFX Tool is what you're looking for if you're in need of improving your PUBG visuals without the headache of manually reconfiguring your smartphone. All you have to do is pick which game version you'll be playing, and from there select the resolution you like, frames per second, and the type of graphics you want displayed. Once you've finished setting up your preferences, all you have to do is launch the game from within GFX Tool. Easy peasy.
Depending on the kind of Android terminal you're using, you'll notice there are different kinds of improvements. For example, if your smartphone screen doesn't support 1920x960 images, there's no point in trying to manually force it, but you can still add in other device-supported improvements that work for you.