Regarding the the tax rate question, marginal rates in the top income bracket in Ontario and Quebec are 53% and 54% annually (federal and provincial combined)
That being said I think the tax rate issue is heavily overplayed as good accountants help them get around a large portion of this.
I think the actual difference after all the shenanigans comes down to be closer to a 10-15% difference which definitely matters isn't as wildly impactful as some people make it out to be. Everyone's city has other advantages sell those as well.
If the highest in the league is 54% (I have no idea if it is) the difference from top to bottom is far lower than 40%. The highest US tax bracket, which pretty much all NHL players fall into is 37% so even in states with zero state tax the difference would be 17%. Its obviously not that simple as US tax rates are marginal. Then some cities have income taxes. Then there are the jock taxes. There is quite a bit of nuance in tax law especially for athletes. The point being no players effective tax rate is anywhere close to 40% more than any other players effective tax rate.