td05 may work alright. mate uses a externally gated one on a ca18. its not too laggy, bit under 4000rpm i reckon (3800??).
so this may work alright on a rb20. shouldn't imagine it'd make quite 210rwkw but it'd be responsive. but realistically your not goin to get much "low down torque" from an rb20
in my opinion, 4000rpm isnt really that laggy, depends what your using the car for but you mentioned not drag/dyno. a car will be quicker on the track with more average power (area under the curve on dyno graph) rather than peak power
a slightly laggier turbo is better (in my opinion) for street driving anyway. uses less fuel, more forgiving in the wet, etc.
remember boost is only a clutch kick away