Laptops and their charging are complicated.
Most laptops adaptors can signal to the laptop how much power is available, so the laptop won't take more than that. If you connect a laptop to a lower-rated adaptor, the laptop will limit the rate of charging of the battery so that the adaptor isn't overloaded.
A laptop will usually take much more power when it's charging its battery.
The computing part of the laptop will take more power if the display is brighter, or if the processor is doing more work. If the power that the computing part is taking is more than the rating of the adaptor, then the battery will be discharging rather than charging. That can happen briefly as programs, or the whole laptop, are started up or shut down. If large amounts of computation are happening, that will increase the power, so running a game with lots of graphics can often make the laptop use more power.
If the laptop is connected to a low-power charger, the processor may be slowed to reduce power consumption. Also, it may be impossible to turn the laptop on with a low power charger connected, and no battery fitted.