the turret of KT is surely a soft-spot that I'll always target it with any kind of weapons (AT gun/bazooka) unless I got the 76mm gun which 2 shots a KT in the side, don't ever try to challenge a KT frontally or to let it have any chance of running away (because when it seek revenge you're done). Somehow curiously the M9 zook is the most effective weapon against a KT as 3 well-placed shots would destroy it.
when shooting at pzIIIs with 6 pounder frontally, shoot at the turret, hull is easier to hit but usually bad angles therefore cannot 1s1k.
I have absolutely no idea how to 1 shot 1 kill stugs with a lower-calibre gun as you often need two shots even to the rear.
panther G is a tough nut to crack with a 75mm gun as you cannot one shot it from the side with good angles, if it is frontally facing you (the hull), check whether you can shoot at the side of turret, else, don't waste your ammo.
When you shoot at a crusader III with a 50mm gun I do not advise shooting at the turret.