Veuscan's Raw Data

Image gamma value is defaulted to 1.0 for 48-bit rgb data and that for 24-bit rgb sample is 2.2.
It is normal that raw data saved with gamma 1.0 will appear much darker.

Raw data in 48-bit RGB

Raw data in 24-bit RGB (or AUTO)

The non color managed image with Epson Scan  is slightly darker compared with raw data using Vuescan set to 24-bit mode, and that the white point Lab data are ( 91,1,4) and (93,1,3) respectively.

No color managed rgb  (24- or 48-bit) output with Epson Scan

Choice of Gama
In general, best choice of gamma is between 2.2 to 2.4 for scanning at 8 bits per channel (24-bit per pixel).
Do not use linear gamma (gamma=1.0) unless you are working with 16 bits per channel (48-bit per pixel).
Gamma 2.4 is closest to perceptual space.
More than 2.4 (up to 3.0) may drop too much highlight.
Less than 2.2 may introduce loss of detail in shadows.

Choice of File Type
TIFF or BMP, depends on supported formats of your platform. Do not store it in JPEG for image to be used for profiling.