I am finishing up my road bike, and I am confused about cassette ratios.

What is the significances of cassette ratios? I see that a 9 speed cassette will have different ratios. For example, you can buy a 9 speed cassette with ratios: 11-21; 11-23; 12-21; 12-23; 12-25; 12-27. Do these ratios make a difference what type of chain and derailer is used?

I purchased the Shimano 7850 wheelset, which is hyperglide compatible. I plan to purchase a 9 speed cassette for wheelset as my group 9 speed, Dura Ace 7700.

Thank you for taking time to read this and any help provided.