what combination of resistors would provide the smaller uncertainty in an equivalent 1000 ohm resistance?

Answer 1

You, like most others here, need to work on your GRAMMAR. Your question is ambiguous also.

If you are thinking of a combination of series connected verses parallel connected resistors there is no difference.

If resistors have the standard Gaussian distribution than the more resistors you have, the lower the uncertainty will be. Unfortunately purchased discrete resistors tend to have non- Gaussian distributions so this will only help so much.

If you can select the tolerance of the resistors, then, of course, use tighter tolerance resistors.

If you are speaking of integrated resistors in an IC there are a multitude of various issues, go with poly or tantalum resistors larger in size. Lay them out in a common centroid manner.

I could go on but you really need to sharpen your question.

Answer 2

Agree with above.
And don't use the word "uncertainty" when you probably mean "the smallest error".