There's a Samsung app called " Goodlock " ... it does some cool things to Samsung devices to customize your Android experience. In Goodlock there is a sub app called "Homeup"... it customized the home screen and app screen and it also has a feature that let's you customize the size of your icons on the home screen. Try that first. If it still has funny differences in the app sizes try to download a new icon pack from Galaxy Store and apply it. If your icons are all the same size now that means the icon pack you were using did the little changes with an update or something. There's tons of icon packs that are free and there are many that you must pay for but you will find one you like, I'm sure of it. Hope this helps!!
