"The "right" instruments and vocals for Bach cantatas will always be a matter of discussion and ultimately of taste. Arrived wisdom is that the small ensembles with instruments from Bach's time and male altos ("countertenors") or even boys for sopranos are the best way. Certainly, it must have sounded more like that in Bach's days. But he did not have the choice of today's warmer, softer instrumental sound, and despite his vehement protestations to the Leipzig city council, he had no budget for a large orchestra.
While it's understandable that some people demand performances to resemble the original sound, I prefer the more agreeable, more instantly "beautiful" sound of modern instruments and female singers. In that category, Rilling's cantata recordings are right up there with those by Karl Richter. The soloists do a great job. The orchestra has "swing", sweetness, consolation, wherever the music asks for it. And the chorus, though somewhat large and intransparent by current standards, sings quite beautifully in many of Bach's dramatic and subtle pieces.
I listen to Helmut Rilling's recordings of the Bach cantatas with great enjoyment and without the feeling of hearing anything other than Bach's genius."