If your Toshiba set top player refuses to play DVD+R discs, it probably won't play DVD+R DL - no matter whether the disc identifies itself as +R DL or -ROM. (You could check whether or not it is supposed to support DVD+R media at
DVDplusRW.org: Compatibility and
VideoHelp Player Compatibility List. It will probably be a while until information for +R DL compatibility becomes available.)
The test I mentioned tested 80 devices of which 23 were set top players, including 1 Toshiba player: the SD-140E. This one
did play the DL disc.
To Q1 and Q2: you won't be
burning in DVD-ROM format. The disc will be a dual layer DVD+R DL either way. The only difference is that with the bitsetting trick, the disc will
identify itself as "DVD-ROM" (little white lie) instead of "DVD+R DL" (true) to the playback device.
