Best will be the highest you can get with no hardware sensor jitter, no sensor smoothing and lowest input lag.
XIM performs better with higher DPI, lower XIM sensitivity, no interpolation.
e.g. G402 can go up to 4000DPI, but at 2000DPI has no hardware jitter sensor performs better overall, then this might be the best DPI for XIM, cleaner and fast the input signal is better.
3200Hz - 4000Hz range is recommended from some users because seems to work better with aim assist. But Aim assist is a coin toss, you might need more or less. 4000Hz IMO is a happy medium.