Ctrl + shift + R would solve your second problem at all times.
And I don't think your first point is quantified correctly and I am sure there is no data to back it up. But I understand the appeal of trying to quantify your personal experience.
I can back up their first point a tiny bit with regards to canvas. The primary product of our company is heavily canvas-based so I’ve always noticed that canvas on Firefox on macs is slower than on Chrome but it used to be in the 2-3x range and nowadays is more in the 1.5x range. They’ve made great improvements and I’ve never noted anything close to 5-10x slowdowns.
On Windows Firefox and Chrome canvas has performed equally well at least for the past ten years. Got no data for linux tho.
And I don't think your first point is quantified correctly and I am sure there is no data to back it up. But I understand the appeal of trying to quantify your personal experience.