Electronic circuit (green boards) stack is set to 20 pcs ... is driving me insane, anyone know how to solve this problem? Re-stack mod doesn't help. Anyone with a solution?

I guess you did not stumble on the magic hidden solution.
Re-stack actually can change it. All you have to do is enter your desired stack size in the 'Production machine stack size' that somehow affects the electronic circuits and solves the annoying issue. However now assemblers and furnaces and pretty much everything in the Production menu will have that stack size which will result in having 100 Fusion reactor in a one slot chest so I do not recommend having it higher than 100.

The electronics stack size in Krastorio2 is by default 200, if you haven't changed it in the mod settings. If you're getting a different stack size, it's probably another mod that does that.