Where have you read that Pilsner malt is the most fermentable malt? I’ve honestly never read that and it’s sort of a blanket statement. “Pilsner” malt is very different depending on where it’s grown.
I would think that standard American 2 row, and American Pilsner malt would be pretty similar as far as fermentability goes due to them having pretty similar enzyme profiles just slightly different lovibond.
Just going by what I was told, and what I've experienced firsthand. I share my beer (neipas mostly) with the owner of a local brewery pretty regularly. I switched from Rahr 2 row to Pilsner malt for 1 batch to try to lighten the color a bit, and I couldn't figure out why the Pilsner batch fermented down to 1.012 vs 1.018-1.020 which I was getting consistently with the Rahr. He told me that Pilsner malt was most likely the reason, since it's the most fermentable malt. Made sense, since my only change to the recipe was swapping in Pilsner malt for the 2 row. I took it at face value. Also, Rahr was definitely more hazy than the Pilsner and had a fuller mouthfeel.
That has not been my personal experience. I always thought diastatic power was more important when dealing with multiple grains, especially when using grains with low DP, which can't convert starch to fermentable sugars? Isn't mash temp was more important when predicting FG, and in turn, residual sweetness?What? Dude.
North American 2-row is a low-flavor enzyme bomb that will dry out far beyond a reasonable Pilsner malt, due to the higher Diastatic Power. 2-row usually has like double the enzyme content of continental Pilsner.
Furthermore, residual sweetness, if you mean unfermented sugar, would depend on the yeast.
If you are talking about some 2-row that is kilned to a "Pilsner" profile, sure. But there's so much sideways here . . . .