Samsung Smartphones: How to customize apps icon size?

If you want to make that change on your Samsung phone, just touch and hold an empty space on the home screen, and then tap on the home screen settings icon. You should see two selections Home Screen Grid and Apps Screen Grid.

Tapping on either one of those choices should bring up a number of choices to change the ratio of apps on your phone’s home and apps screen, which will also change the sizes of those apps. Depending on which phone you own, the home screen grid choices could be 4×5, 4×6, 5×5 and 5×6, while the app screen grid ratio choices are 4×4, 4×6, 5×5 and 5×6.

Please refer below screenshots for steps: