The values returned from the raster and raster band describe properties should match the strings expected as inputs for working with rasters in GeoProcessing tools. For example:
desc = arcpy.Describe(tiff)
Returns the string 'U32', which does not match what is needed in, for instance, the CopyRasterManagement_tool. The string to set the bit depth to U32 is "32_BIT_UNSIGNED", which requires creating a lookup in one way or another rather than using the output of Describe as input to a GeoProcessing tool.