[Franek Grabowski]

I am not aware of Bader lacking actual victories, though no doubt his choice of Spitfire VA was weird one and reduced chances of scoring victories.
Cannot say anything about Stanford-Tuck.
Johnson's victories are listed on Wiki with an attempt to attribute losses. Does not look spectacular, I would say about average.

Basically, the problem starts after the Battle of Britain, where there are no details of German losses or operations in general. In the effect it is extremelly hard to match combatants of both sides. Funnily enough, it looks that JG 26 attributed all aircraft downed in their area to their pilots, not knowing actual reasons of losses. So a kind of hidden overclaim.