The type of disk can be either -R or +R (if you use +R you should use bitsetting, but you have to use modified firmware to get it on the 3540, i've got dee's one from here and works like a dream).
Good DVD readers should read either -R or +R, but +R with bitsetting works with more than normal +R.
All your disks will be region free unless you tell your software to do different. There may be issues with PAL or NTSC if you want to send your disks overseas but otherwise no region problems for you.
If you were asking about DVD format as in DVD movie or data then you'll have to give more info on what you want to do.