To maintain a stable club face through impact, there are many opinions amongst many good players as to how to do just that. Some promote the opposite hand low method. Others promote the claw grip or long putters, etc. Any way you look at it, the purpose of all of these methods is to maintain some square face consistency through impact. I personally think that maintaining a firm top hand with a conventional reverse overlap or baseball grip, along with a straight back straight through stroke that’s not too handsy helps to do that just fine.
Ultimately, the best putters (with any method) do maintain square face consistency with good distance control and feel. Just remember that (as in anything in golf) putting is only part science and a whole lot of an art form. So, don’t get too caught up in the mechanics. Maintain a good, sound simple grip with a rhythmic stroke and let your creative juices flow. But, never forget that feel and intuition are such a huge part of golf, especially when putting.