The Spit Mk.II is currently the only fighter that seems to be getting it's real life performance. All other fighters (not just luftwaffe ones) are somewhat on the slow side, so the Mk.II is usually removed so that the server doesn't end up with a bunch of people flying them in the red team with nobody to shoot at in the blue team or nobody flying the Mk.Is and hurricanes
As for the drifting during taxi, i've seen it reported before but haven't experienced it. Not flying online yet (i spend most of my time testing various things in single player) i can't be sure if its a multiplayer-specific bug, but i've seen various plausible explanations.
The most prominent ones:
1) There's a crosswind involved in the mission and tail-dragger aircraft turn into the wind. Some people report that hangars don't block wind and the effect is noticeable in hangars as well.
2) Incorrect setup/usage of the wheelbrake controls.
3) A combination of both, making it hard to correct the crosswind effect.
I've posted this a million times on various threads so i'll just give you the cliff notes. In short, the sim models brakes the way they are in the real aircraft. For RAF warbirds, this means a single brake lever for both brakes and a differential pneumatic valve operated by the rudders, instead of two completely independent braking systems for each wheel.
To turn left for example, one needs to press the brakes lever (whatever control you mapped to it) and push the left
rudder pedal. Pushing the brakes key feeds pneumatic pressure down the line, the position of the rudder pedals determines how that pressure is distributed to each wheelbrake and as a result, how much each wheel brakes. If the rudder is centered the pressure is distributed equally and both wheels brake the same, if you start pushing the pedals one way then the wheel on that side of the aircraft will brake more and you will turn to that direction.
In other words, if you have a rudder pedal controller with differential toe brakes plugged into your PC and mapped as such, your toe brakes won't work because the aircraft doesn't have such a system. It's like giving a prop pitch change command in a tiger moth with its fixed pitch propeller, or pressing the "open bomb bay" keys in a fighter: nothing happens because they don't have such a system installed. You will need to press the brakes key and deflect your rudder pedal (just like you would do while airborne) to get differential braking instead.