Need more information about screensaver

[IrishMerlin 0]

I'm using Emby web app, version 4.7.11.0

I searched the Emby (should it be lowercase emby?) forum and googled, but didn't find what I was looking for - apologies if this was already asked:

1. I go to "Configure Emby" - or "Manage Emby Server" -> Clicked on "Display" -> I see Screensaver with Logo, Backdrop, Photo - that made me smile. But how do I implement that? I couldn't find a good Knowledge Base regarding screensaver. So... based on the forum/google research, I confirmed that I'm not using windows screensaver at all. I do not have computer go to sleep, etc. If I selected the Photo screen saver, after 5ish minutes, the screen goes to black. If I were to change the backdrop screensaver, do I need to provide images somewhere? -- Basically I need guidance on this.
2. Is there a way I can shorten the delay before displaying screensaver? Again, based on research, I found one person said to check screensavermanager.js, but the forum ended without much details. I looked into screensavermanager.js (I know some programming) and had to use beautify for JS and didn't find anything related directly to 5 minute or whatever minutes to modify. Perhaps I overlooked, but is there a way to change the duration before displaying screensaver?
3. Is there a detailed documentation about the difference on Logo, Backdrop, Photo screensaver and how to use / build images / etc for each one?

Basically I'm asking for ELI5 on how to implement screensaver. (ELI5 = Explain Like I'm 5 years old).

Much appreciated.