It looks like the Scout camera returns multi-byte data in little-endian format. This is somewhat common but the DCAM specification requires multi-byte data to be transmitted in big-endian format. Since the toolbox is expecting big-endian data, it is not able to correctly scale the image for preview.
Since this is somewhat common, the toolbox does provide a workaround. When you start MATLAB issues the command:
>> imaqmex('feature', '-useDCAMLittleEndian', true);
This tells the toolbox to expect the data in little-endian format. There could, however, be one further problem. The DCAM standard does not specify which bits are supposed to be used within the multi-byte data. That is, for a 12-bit camera the data could range from [0 4095] or [61440 65535] which results in a big gap between 0 and 61440. The toolbox has no control over this and may, therefore, still not be able to scale the image correctly for preview. The data returned by GETSNAPSHOT or GETDATA will be correct.
As to the available formats, the camera does have Y422 formats available. In these modes the U and V components are set to zero by the camera. This is presumable to allow client applications written in a language like C++ to use a common display routine across different camera models.
The formats that start with "F7" are "format 7" modes. According to the DCAM specification format 7 is the "partial scan mode". It allows for setting a hardware ROI which can increase the effective frame rate of the camera. It also has some other properties which can be useful in some situations. The Scout manual refers to these modes as "flexible" formats and has more information about what this means for the Scout cameras.