The issue is with your computer or playback set up, not how you are burning or what format (unless youre doing that incorrectly). We need more info.
First off, dont use Windows Media Player for anything…not even WM files. Download a copy of VLC and use that.
Replicated discs are Not DVD-r or + r, they are a separate format called DVD-VIDEO and are physically pressed
DVD-R can before +r so you have that mixed around.
DVDSP, in fact, caused several errors some years ago which is why you were told to use Toast. Toast has never had any measurable issues.
Bottom line is that DVD playback on a computer can be spotty – always has, always will be depending on the set up, and playback software and how well the end user knows computers. If you expect to send out tons of discs and expect everyone to get flawless playback experience then it just wont be happening. DVDs were meant to be played on Set Tops on your TV.