Will a contoured wrist rest mess up my mouse cursor tracking?

No. Modern optical and laser mice track based on surface texture and relative movement, not distance to the pad. A contoured pad that’s thicker under the wrist but flat under the mouse is fine. The real issue is if the pad has bumps or slopes where the mouse sits—most wrist-rest pads keep the mouse area flat. For 99% of pads, tracking is identical to a flat pad.