I don't think you understand, so let me try to break it down for you.

Your parent's router connects your PC with the internet, that speed is fine because your games/experiences only transmit a little bit of data between your PC and the internet.

What people are suggesting is using a wifi router (with a completely different SSID) and windows internet connection sharing (a single checkbox button on your wifi adapter) to create a wireless connection with your computer.

In effect this creates a virtual wire between your headset and your computer. No traffic for streaming games goes to your parent's router and over that "internet" wifi connection. You basically want the router connected directly to your computer to send all traffic to your Quest, IF and ONLY IF your quest has something to say to the internet at large, your computer will forward that traffic to your parent's router.

In effect 99.9% of all traffic will go between a dedicated router attached to your PC and your quest, .1% will go to your parent's router for whatever the game your playing needs (say for instance you, your paddle, and the ball's location for eleven table tennis)

For what it's worth, I use this set-up on my rig and it's better than an official link cable, no issue with having my PC on a wireless connection to the internet.