65W laptop power adapter and 90W are mainly configured according to the power consumption of your notebook. Generally, the integrated graphics card is equipped with a 65W laptop power adapter. The discrete graphics card needs additional power supply, so it generally needs 90W. Of course, some use low power consumption. CPU, such as 25WCPU, 35W, 45W difference, these are the maximum power calculated by the manufacturer based on the power consumption of the notebook at the beginning, and then equip your notebook with an adapter.

The 90W adapter can replace the 65W laptop power adapter, as long as the interface is the same, but the 65W laptop power adapter instead of 90W may sometimes cause insufficient power and cause automatic shutdown.
Generally speaking, the larger the wattage, the larger the size, because the adapter is actually a coil that converts 220V to 19V, and the size is determined according to the current. The larger the watt, the larger the output current will be.
Generally speaking, the power consumption of a notebook is to decide whether to use a 65W laptop power adapter or a 90W adapter power supply, but it does not mean that the 65W laptop power adapter power supply will not be used for the 90W laptop power adapter. It is just that the power is not up to the machine. Some functions cannot be activated when using certain functions, such as the power supply of an external device. If the original requirement is a 90W power supply, but you are using a 65W laptop power adapter, the external device will not work properly. However, in some cases, external equipment is not required, so it is very convenient to choose a compact power supply of 65W laptop power adapter.