Unlike the Amiga. An XBOX-1 only outputs interlaced screens via RGB SCART. This means that it is pretty much guaranteed to work well with any second hand 4:3 LCDTV.
I thought the majority of XBOX-1 games were designed to be wide-screen though?
If you want to use an LCD monitor and not an LCD TV and use the VGA input you will have to create your own modded cable and switch to NTSC HD to get anything to work. The XBOX is not flexible enough to output panel resolution so you will have scaling issues. PAL will probably not work because most panels cannot do 50Hz. I've never successfully done this... but there is lots of info out there on how to try.