Apparently most of us prefer the digitigrade legs.
When I think of Ferals seamlessly switching modes, I think of werewolves in Skyrim. They fairly easily go from two-legged walking to four-legged running.
One person said that if they're kicking then human-like legs make more sense and I disagree.
Think of a kangaroo, they balance on their tails to kick.
Cats use their front legs to hold onto something, then use their back legs (and claws) to rip into them and can then easily let go and run away.
Since dogs lift their legs to pee on things, it's not hard to imagine their knee extending a bit to kick their opponent.
Just a few examples off the top of my head how even with digitigrade legs the ferals would have no trouble fighting.