Start Goff if his thumb is good enough. He's the starter and, on balance, the better QB even if Wolford adds a dimension to this offense with his legs that Goff cannot.
But if Goff's thumb isn't yet letting him grip the football at full strength - and I imagine that might well be the case - I don't want Goff anywhere near the field. He fumbles too much at the best times. Wolford has the team rallying, has proven he can manage the game and make just enough throws, has shaken out the nerves now, and still has the "unpredictable / no game tape" advantage over anyone he faces. We can't have turnovers in the playoffs. If Goff's thumb is weak, I don't trust him enough to hold onto the football.