White fuzz on soil after repotting, mold or pests?

Mealybugs are usually on the plant, leaf nodes, stems, and undersides. Soil mold usually sits on organic bits on the surface. Use a toothpick and see if it is growing across the soil rather than attached to an insect body.

If it is just on the soil, improve airflow and let the surface dry. Scrape off the worst patches. Mold is usually a moisture and airflow signal, not a disaster.

Fresh bagged mix can carry spores, especially if it stayed damp in storage. That does not mean the mix is bad. It means the conditions let the fungus show up.

Check for gnats too. Moldy damp soil and fungus gnats often enjoy the same situation. Sticky traps will tell you if adults are around.

Look at the texture. Mealybugs look like little cotton bits with shape and they may appear in clusters on the plant. Mold looks more like a soft film or fuzz spreading over soil particles.

I sprinkle a thin layer of chunky bark or pumice on top after cleaning it up. Not as a cure-all, but it helps the surface dry faster in my cold room.