a mouse+keyboard combination is technically better than the keyboard alone, since you can have analogue steering. only thing is it will feel totally unnatural when you are first learning. however when you get used to it, it's quite an amazing control method, turn as quickly as you want and with dead accuracy.
im a mouse racer and have no problem keeping up with wheelers, even have 2 WR's outright
however i will say..
some people also use the up/down motion of the mouse to enable analogue acceleration and brake (and at the same time, left and right on the mouse to steer), i would advise against this as it simply gives the mouse too many things to do and your racing will no doubt suffer from this. also, others use the mouse buttons for accelerating and braking.. but for me this also feels like again the mouse hand is doing too much
the answer? use A for accelerate, Z for brake, X for clutch, space for handbrake. this gives your left hand complete control over all the speed related controls. you can easily blip the throtte while braking, or even blip the throttle while braking and using the clutch, the finger which is used for brake can move across to hit both Z & X together, etc.
this leaves your right hand free to steer with the mouse, and shift gears with the mouse buttons.
that's the setup i use, and i personally havn't found one for this control type which is better! hope this is helpful
tak