I doubt it could be negative, as you already have ala in your body, but it may not be beneficial if you are insulin sensitive, at least in improving sensitivity. There may be some metabolism boosting effects. (Insulin sensitive rats were shown not to increase insulin sensitivity from its use, but there was some apparent fat loss without a change in LBM.)
It is believed to have a similar effect as metformin, a diabetic drug. But I do not believe it has the same half-life though.
The r isomer is way superior to the s isomer, or the racemix commonly sold, and it looks like the s may undo what the r does. I have no knowledge of the different forms you are talking about though.
I know Barr has said taking this supplement is best after working out, with Surge. This is not to affect the insulin boost, but the r-ala will take longer then the Surge to take effect, so the benefits from the r-ala will occur after the boost in insulin. He has also mentioned that research has been done mostly on obese and insulin resistant rats, and diabetic humans.
Being a powerful anti-oxidant may be enough justification in taking this supplement.
The only information I can find on the potassium r-ala are the advertisements. They say that supposedly bonding r-ala to potassium will increase bioavailability.
And the R-dihydrolipoic Acid is supposed to be the reduced form of r-ala, and is supposed to be more powerful. (I wonder if this would negatively affect bioavailability.) I still have not found any serious information, outside of advertising, about this.
Until I learn more I would stick with r-ala.