Hi! Welcome to the Samsung Members community!
For customizations, hold down on a blank spot—it will zoom out and offer Wallpaper and style, Themes, Widgets, Settings.
Go to settings- homescreen- here you can change the app sizes
You can, however, download GoodLock for more advanced options—Home Up, Keys Cafe, Wonderland, Theme Park, and more.
https://apps.samsung.com/appquery/appDetail.as?appId=com.samsung.android.goodlockThere's quite an extensive amount of options, so be sure to look up tutorials.