Take my apologies for the such a long delay in answering. I have created both mega menus using Static Block.
All you need is to create the static block that will have the columns/rows layout you need and use Menu item list VC element to add menu items and subitems. Once block is created choose it for the first menu item in your menu, choose mega menu design and mega menu columns number to set width of the mega menu http://prntscr.com/iliz8r
Let me know if you need to re-create any other menu item from our electronics demo as example.
