Hello 4pouiu,  there is no best practice that I can find more like caveats. The KB article you mention is a good caveat as you can see there may bee issues with performance when hitting top level directories with many files and folders. obviously it is good to still use general file permissions as much as possible to grant access only where it is needed then apply ABE where appropriate down the access chain.  the only real issue that I can find on this is that ABE can slow down performance. so the best practice would literally be try not to put it on top level directories and understand that as file count grows it can slow system performance.  a few references for your convenience: [URL]  [URL]  [URL]
I found an KB, but this does not inform numbers, such as how many share , files or directories can be used when the ABE is enabled   462981 : OneFS: Access Based Enumeration (ABE) enabled on directories with high file/folder count causes high LWIO CPU usage and poor performance [URL]   anyone know any documentation where we can have more information on ABE
I client asked me if there is any recommendation or best practices when we 
enable the Access Based Enumeration tool