If your two machines connect to the Internet directly (the device at the other end of your ethernet wire and the one that the WiFi from your laptop connects to), then the only way you can create this imbalance is at that point where the two paths meet.
This means, you either configure your 'router' device or the WiFi access-point to limit laptop bandwidth. But, the real trick is in being able to give the laptop full bandwidth when the PC is not taking any.
If you want to bias towards your PC, one way is to make the PC route your laptop's access to Internet. This requires you the keep that PC between the Internet and the WiFi access-point. That is provided, you can really do such a physical placement.
If that can be done, you would just throttle the WiFi access-point bandwidth from your PC when you are using Internet from there. And, at other times, leave the throttle open. Again, a downside to this is, your PC would remain up when laptop wants to reach Internet -- unless, you do more trickery.
Expected present wiring,
PC == Internet-Device == WiFi Access Point == Laptop
Internet-Device == PC == WiFi Access Point == Laptop
I refer to the Internet-Device as 'router' in the above description.
And, expect that it is physically different from your Wifi Access Point (WAP).
If that is not the case, you need to figure out if-and-how the combined Internet-Device can be configured to throttle the WiFi bandwidth.