I'll let Wikipedia answer one question:
Almost all DVD-Video discs use the UDF bridge format, which is a combination of the DVD MicroUDF (a subset of UDF 1.02) and ISO 9660 file systems. The UDF bridge format provides backwards compatibility for operating systems that support only ISO 9660. Most DVD players read the UDF filesystem from a DVD-Video disc and ignore the ISO9660 filesystem.
So to reiterate the point, and because I'm sure someone's mentioned this to you before, the device reading the disc (computer, DVD player, etc) uses the best/most preferred file system available on the disc. Why would it bother to read file information from both file systems?
To quote you in your above post:
So if the 1999 ISO setting really isnt that compatible then i think i already would have problems playing them unless it just only reads the udf system if it cant read the iso file system.
â€¦given that devices are going to use the UDF file system info to read the disc, you wouldn't know if the ISO 9660 settings you apply will cause a problem on systems that don't read UDF.
But no, :1999 isn't supported when a DVD-Video (or DVD-Audio) playback device has to read the ISO 9660 file system. Most systems that CAN read :1999 also read UDF, so there's no reason to worry about those settings. Leave them beâ€¦or change them to whatever you want. Turn :1999 off and see if ImgBurn complains when you add your extra files.