I made the Slide Deck preset, so you’re in the right place. 
Slide Deck was created during the pandemic as a way of shrinking PowerPoint presentations and screencast tutorials and video conferencing meetings into the absolute smallest file size possible while retaining sharp quality for static images like slides, hence the name. This allowed remote education lessons to be accessible to people with slow Internet connections, and allowed up to 20-minute Zoom meetings to fit into a standard MP4 file that was still within e-mail attachment size.
The export preset compromises video quality on purpose to be no better than webcam footage, because that is the highest quality source it expects to process. So it optimizes bitrate to webcam quality for moving video to keep the file size small, and only aspires to reach “good enough” for quality. This was an intentional design decision. If you need higher quality video, you will need a different export preset.
As for static images, they should be nearly perfect, as the preset takes major compression advantage of seeing the same frame over and over again.
For more information: