Hi, for sure if the green is very quick, then everything is accentuated, the break, and the amount you have to take off for downhill.
So for distance on legend greens I use 25 % as the amount to take off, so a 30 foot putt on a flat green is gonna be hit for 22.5 feet.
Simply speaking for championship I take off a further 10%, so I would hit 20.
But if there is any downhill involved then you have to take off even more.
The putts that have break will break more simply because you are not hitting the ball very hard and therefore the slope and elevations will have more effect on the slow moving ball.
Think of a championship green like a snooker table, and get a feel for how hard u hit that ball to travel 12.5 feet.
Ian Woosnam used to practice his putting in his socks on a snooker table, a very similar speed to the Pro greens.