Does object transform matter in game size?

Just asking if it’s smart to keep object’s size as a full number instead of decimal point number.

In general no. all numbers (position, rotation, scale) of a transforms are always float. This will not change if you put in a whole number or a floating point number. It will always stay 4 bytes of floats. In general this is also something that you should not concern yourself with regarding optimization (except for some really really rare edge cases). If you have concerns for your game size (be it build size or RAM usage) you should rather take a look at the assets you use and if you can reduce them in size or use more dynamic loading/unloading of unused assets (for RAM optimization)