OK it's finally time to clear up all the confusion. I was totally confused about all this recently so I emailed Castrol Technical division about it. Here's what came back...

Castrol TTS is now Power1 TTS, just a rename.
Castrol R2 is now Power1 Racing, another rename, Power1 TTS is NOT replacing it, they're both different oils although very similar and can be mixed because the technology in them is so similar. He did say that he normally would not reccomend mixing 2-stroke oils but since they know the exact technology in both of these oils, it's not a problem.
They're both fully synthetic and can be used as premix or through an oil pump.
The guy said he would have no hesitation in using either in a road going NSR but if you want the ultimate then go with Power1 Racing(old name = Castrol R2).
I have a bottle of Power1 TTS and a bottle of Power1 Racing. They're both coloured red and smell identical. The spec charts(viscosities, flash points etc..) for both are identical too.
Castrol do a huge range of oils and at times it can get confusing as to which one best suits you.