For example, you can’t drag vertices anymore in edit mode when you occupy the drag by border select. Happy modeling 
And as told, border select exists in nearly all other editor types too. Which also needs to be checked and fixed. I ended in two handful conflicts already after just five minutes toying around. And fixing those conflicts will create other conflicts. The keymap is a big can of worm when you touch the wrong end. And this is one of those wrong ends, unfortunately.