The overlapping tracks on top and bottom acts like a parrallel plate capacitor with capacitance C directly proportional to Area of overlap.

Exact! But your methode to shift one track a bit, so that they do not OPTICALLY overlapp, does not at all improve situation! Why? Because after this slight shift both tracks will still PHYSICALLY overlapp. Means, the electrical field lines still end on the other track, the stray capacitance between both isn't decreased at all.

Only the routing of tracks over solid ground plane will relevantly decrease stray capacitance between such copper tracks!! And if they are routed on the same layer the area between both tracks must also be filled by ground plane.

Kai