They steal people’s domain names, there have been many reports over the past couple of years. If anyone has a domain with them it’s recommended to transfer away. They used to be good, but I assume anyone still recommending them isn’t up to date on their behavior.

Nvidia Optimus and the selector I’m using is MATE Optimus

On my Linux laptop with a Nvidia card, there is a Nvidia program which lets you switch between dedicated or on-board graphics, or on-demand where applications can request the graphics card. Before that the dedicated card was always on. I’m on mobile at the moment, but there is an official Nvidia website with drivers and other programs to control this. I assume the same for AMD, but I haven’t checked.