when are .cue files really needed?

Hi, I read .cue files are not needed when a game consists of only one bin or ISO File?
What If that .cue File describes that Single bin File plus some audio Tracks?

If the game has a bin file and audio tracks then you definitely need the .cue file.

Most modern emulators will work fine with a bin/cue file combination, if you are using a frontend for your emulator you can configure it to show only the cue files.

You mean when there are audio Tracks Files additionally to the bin File then I need the cue File, okay.
If the cue File has audio tracks described, but there are No audio tracks in the form of Files Besides the Single bin File then I don't need the cue File?

And what are sbi Files? When are they needed?

Last question: I'm Testing Parasite Eve II for Playstation 1 with EPSXE Playstation 1 emulator for Android, is it correct that the Dialogs between Eve and other persons in the game are only in Text and completely without speech?

sbi files contain subchannel data, yes you need those. When it comes to Playstation 1, you will commonly find SBI files in European versions of the games.

In any case, please keep the cue files. They are so small you are not wasting any space.

As for Parasite Eve 2, I have not played it in a while but I think everything is correct. Just text, no voice.