Most DVD players do in fact support dual layer playback. I've actualy yet to come across one that doesn't, but I'm sure they exist. (VERY early models) Truth is, most factory pressed DVD movies are ON dual layer disks. Unfortunately, most of us use software such as DVD Shrink to make our backups fit on 4.7 gig media as dual layer is still pretty cost-prohibitave, so finding real-world reporting on peoples successes and failures with playback using dual layer is still a bit limited and will probably require some pretty intensive searching on your behalf. The DVD section under the media forum may help a LITTLE, but keep in mind that it is primarily ment to be used for posting SCAN results, NOT playback results for, "stand-alone," or, "set-top," type DVD players.
Reguarding book-type setting, each disk has a book-type bit that tells the machine what type of disk it is. SOME players only like disks that are recognized as, "DVD-ROM," type. If you do a search here on, "Booktype setting," you'll find SCADS of threads. Here's one for example:
Lastly, I'm pretty sure that if you bitset a +RW (Re-Writable) disk to DVD-ROM, you will NO LONGER be able to re-write the disk. Therefore, if your standalone REQUIRES bitset disks, you should be burning standard +R's as bitsetting +RW's defeats the purpose of using re-writeable disks in the first place. (+RW media costs more than +R becasue is IS re-writeable, and also it burns slower. Only 4X in most cases.)