WiFi is great for browsing websites but for streaming videos, it’s best to use cat5e cable connected to home router.
Devices can sometimes update app’s or download software updates in the background unknown to the user, this can effect
The speed of the WiFi when performing speed tests or effect other users on the WiFi.

You can install an App called “WIFI ANALYZER” which will allow you to view the signal strength of your wireless in each room.
The App will show you neighbors wireless routers, this will help you select the cleanest frequency for your own home router.