Wire/contact plating material

Typical M22759/32 is tin plated, but some other mil-spec wire (and Spec 55) can be had in silver or nickel plating.

Also, many contacts and battery terminals can be had with tin, nickel or gold plating.

Besides k-type thermocouples, what are the different use cases of the various plating materials for motorsport?

Have a read through this webpage. It should have most of the information you are after. https://www.rbracing-rsr.com/wiring_ecu.html

I've read through the data sheets for several OEM connectors. One interesting thing I noted is the tin plated contacts are typically rated for 10 mating cycles. But the exact same contact with gold plating is typically rated for 100 cycles, and also usually has a higher temperature rating.