I'm afraid that the type of ball ain't gonna matter whatsoever on fast greens. It is round.... which means it's prone to the forces of gravity simply by design.
The impact-force during a putting stroke matters greatly.
One of the biggest misconceptions with putting is that every stroke needs to honor the dynamics of acceleration. Now if you're 10 feet below the hole, putting uphill - this certainly holds true. You would prefer that your putting stroke be both deliberate and positive, i.e you've picked out the proper line you want the putt to start on and you make a positive, accelerating stroke based on the break that you've read into the putt.
But downhill putts on quick greens are vastly different.
There are countless times throughout a season where I find myself standing over a downhill 20-footer that is lightening fast. It might not just be the contour and slope of the green, but also maybe the wind factoring into the equation. Our greens are generally fairly quick and there's plenty of undulations in play. And we won't even go into the grain of the greens... downwind, down-grain, downhill.... we're talking the trifecta as it relates to difficulty.
Numerous times, when I'm standing over those downhill 20-footers - I'm not thinking in terms of "acceleration" as it relates to how I deliver the putter face to the golf ball. But more of a gentle "nudge." I'm simply and literally wanting to make a 3-4 inch putt, and then let gravity do its thing. Feel.... touch.... understanding how quick the greens are, understanding how severe the slope is I'm putting on, understanding the delicate dynamics of (hopefully) getting the ball "nudged" on the right line at the right pace and giving it a chance to go in, without leaving myself an enormous amount of anxiety coming back for the next one should it not drop.
That said... 20 feet above the hole on quick greens - yes - you can hit the putt too softly. You can leave yourself with another putt from 8-10 feet above the hole on your next one, being overly cautious.
But... if you really focus on your putting stroke, more aptly the speed of your stroke and how that intertwines with the slope and the speed of the greens - you'll do fine.
Below the hole - I'm thinking in terms of a positive, accelerating stroke.
Above the hole - I'm thinking more in terms of a soft-enough stroke to barely get the ball to the hole, with the outside chance that it might go in.
You need to be flexible in your putting style. A 3-footer from below the hole - positive, accelerating stroke with just enough pace to go roughly 12 inches beyond the hole. A 3-footer from above the hole? I'm trying to gently coax that puppy down there with just enough pace to get it to the hole. And if that means I just simply need to "nudge" the ball - that's what it means.
When putting from above the hole on quick greens, you can be aggressive to your target line without being aggressive with your putting stroke. There is a difference. Figure that out and you're most of the way there.