Correct 2W is on par with 2H with a -1 offhand and -2 MAP for the 2W with damage dice of 2d6 and 2d8.
With two fisted removing a total of -4 penalty and ambidextrous removing -2 penalty (per straight rules) it has the result that 2H becomes the littlest fighter so to speak.
The system I'm writing uses fixed damage dice hence my calculations for those. While one can balance a system with edges/feats/advantages certainly I'm going with a base balance. We (my group with the exception of one power gamer) really enjoy the lack of needing to worry if you're underpowered or overpowered based on weapon choice. Definitely not for everyone though.
I didn't use any mechanisms from P&P, I remember reading it a year or so ago but honestly couldn't tell you anything that's in it at this point. The simulation is starting to veer far enough in terms of basic math and mechanics that it's becoming less applicable in determining odds and percentages for savage worlds mechanics.
One thing I think is important to note is that two-weapon fighting _should_ be underpowered, even with a single edge. Making changes to make TWF more on par with one-handed weapons or even two-handed weapons is akin to giving katanas bonuses just because they're "cool".