When operated in 0V to 1.024V, the VDAC can convert upto 1Msps.
The VDAC is slower in 0V to 4.096V mode because the resistive load to Vssa is 4 times larger. Hence, in this mode, the VDAC can convert upto 250ksps.
This data is present in the VDAC8 component datasheet which can be accessed from the Creator Component Catalog.
The max frequency of the sine wave which you generate depends upon how many points you are using in the look up table.
Lesser the number of points, higher is the frequency attainable. But the sine wave will not be smooth. On the other hand, if the number of points is large, the sine wave obtained will be smoother.
In either case, using a low pass filter at the VDAC output will smoothen the sine wave and eliminate the step-like update in the sine wave.