How many materials per imported object?

Hi, I'm building an asset, a car wheel, in maya (a single object) that aims to have four different materials (tire, rimms, brake disks and brake pads), each with its texture. I'm not sure what to do:

Should I have one object for each material (separate my single object into different ones), or is it ok to have this single mesh with four different materials?

Should the textures be baked to the object before exporting to Unity?

I just want to make sure that I'm taking the right steps in the creation of this one object that is meant to be used in Unity. Understanding the right way to approach it before creating more assets and risking building them the wrong way. If you remember something else that I should know about, please tell me (all info appreciated) If I sound like I'm new at this, it's because I am...and if I have made any ridiculous questions, I apologise.

Thank you for your time!