Scale either shrinks or grows Ui according to the devices screen size, while offset keeps the size of the Ui on all devices. For example, if you create a text button using offset, and you set the offset values to 200 and 50, then it will be 200 and 50 on all devices. However, if you use scale, and made the text buttons values 0.3,0.3 (you cannot use a number over 1, otherwise it would take up the whole screen. So use numbers like 0.1 or 0.3. 0.9 would take up most of the screen), then it will shrink on smaller devices, and grow on larger ones. If this doesn’t make sense, maybe this tutorial might help here. I recommended though you use scale, so that way your UI fits in all devices.
Have a good day!