So volumes seem to be almost the same thing as the scalar fields.
Though for scalar fields you have a lot of predefind microsolvers like advection,gas analisis and so on.
But it seems that you can make something similar using volume wrangles in SopSolver.
Is there a more important difference between them that im not able to grasp?

I'm not expert on the differences, but one I know of is the alignment for sampling. I don't know if sop volumes have an alignment (sampling) setting. Scalar/Vector fields both have alignment(sampling) settings for face/edge/vertex/center aligned sampling. Additionally, many microsolvers do not have a sop analog. Gas projection has a new vdb-only analog in sops, but it is missing many features of the microsolver, such as collision fields and a divergence goal field.