One slope, many possible breaks
A slope does not have a single fixed amount of break; it has a range, because a slower putt spends longer under gravity's influence and drifts more, while a firmer putt fights the slope and holds closer to a straight line. This means the question 'how much does this putt break' has no complete answer until a target speed has already been chosen, which is the opposite order to how the question is usually asked by casual players.
The trade-off in choosing pace
A firmer pace reduces the effect of small misreads and imperfections in the green surface, but it also reduces the chance of the ball dropping if it catches even the edge of the hole, and a miss will finish further past. A softer pace gives the hole a better chance of catching the ball from more angles, but it hands more influence to the slope and to any unevenness the ball rolls across on the way there.
Speed first, then the line
Strong putters tend to commit to a pace before finalising the line, treating speed as the primary decision and the read as something built around it rather than the other way round. This ordering matters because changing pace after settling on a line quietly invalidates that read, which is a common and largely invisible cause of putts that looked well struck but simply missed on the low or high side of the hole.