To such questions the answers are always obvious and elementary
how is this design
Anything "such" in it, the most common design — tiles, menu, sidebar.
Which mesh it is
Left menu with three columns of tiles of goods fixed width, and inside all otherwise menu on the left + one content column + sidebar, and all different widths. Now all we need some strict grid as it was before. Now it is not necessary to cram the content in a pre-drawn grid, and it is necessary to arrange the content as intended, and on this basis to find the net. Now the designer of that website decided to do so, with emphasis on adequate display on mobile devices and PC monitors. In General, in my opinion, the logical approach to this content.
what permissions need models for coder?
It is necessary to ask the coder because everything used to work differently. You need one layout for each resolution, another simply a textual description of a behavior or guideline (if it is under some kind of bootstrap or similar), and the third would be enough for one layout, and then themselves. Advise now one, and in practice you may need more or do not need. I always specify these details in advance, before creating the design.