The 125 NW impeller fits on the 65 pump just fine, the NW diameter is bigger. I only needed to trim back the impeller shaft to make it shorter to fit on the 65g magnet driver.
The 65g pump is rated 23W, when no air was injected, the pump was drawing 19W, after the 125 impeller was installed, the pump was drawing 30W and the flow was noticeably stronger.
But when in both cases airline was wide open, they both draw 16W.
In the case of the 125g impeller, I used my needle air gang valve to fine tune the air intake, basically reduced the air intake to the point that the most foam was produced in the skimmer. At that point the pump was drawing 24W, very lose to the rated capacity. The foam rise was much stronger. Only time will tell how much more it can skim compared to the 65g impeller.
I did notice more microbubbles out of the skimmer but they were never a concern with my sump setup.