I can use the "-Q 1964_10" command for dispcal but I can't use it for dispread. (Or did I miss something? / Is the documentation outdated?)
You save the spectral information in dispread ("-s"), and choose the observer in colprof etc. Note there is no problem with calibrating using one observer, and profiling using another, since (at the end of the day), a color managed application controls the display by making use of the profile, and the profile characterizes the calibrated device. (ie, calibration and characterization are largely independent.)
And (if I use spotread with 1964_10 observer after the FOV10 calibration) can I feed a CMS software with XYZ.10 values?
I'm not sure what you mean by this.
I need primaries and white coordinates for gamut emulation and I think the software assumes XYZ.2 coordinates. I doesn't sounds too good for me.
Generally it's good to work in a consistent colorspace (ie. you want to use a common color "language"). That may be an appearance space, if appearance is being taken into account. Mixing and matching different colorspaces should only really be attempted if you understand exactly what you are doing. [It would be a slightly unusual situation to want to use a different angle observer for source and destination profiles for instance, in that it is typically assumed that matching of the same visual material or image is desired, and that therefore the images will be viewed from the same angular distance. This is one of the problems with the idea of calibrating to a 10 degree observer - it may make the overall color of the screen match some other white point better, but if the actual images details are being observer ate 2 degrees, then 2 degree color matching is what's really desired.]
Or does it effect only the spectral data ---> XYZ coordinates calculations and I am free to use these XYZ.10 coordinates in any softwares where I can't set observer types?
Maybe. I'd use the 10 degree adjusted observer for this though, since it's been optimized to reduce the numerical discrepancy to 2 degree XYZ numbers.
I can't understand how XYZ.10 helps when everything else is based on XYZ.2 but I am not an expert, so...
If you don't understand what the implications are, then don't use it. Graeme Gill.