If using tofu, line a plate with a paper towel. Cut tofu into 1" dice and place on towel-lined plate. Top with paper towels, then press gently but firmly to remove excess moisture. Season all over with 1/4 tsp. salt and a pinch of pepper. Follow same instructions as shrimp in Step 4, stirring occasionally until tofu is lightly browned, 5-7 minutes.
If using 16 oz shrimp or jumbo shrimp, pat dry and season both sides with a pinch of salt. Follow same instructions as regular shrimp, cooking in batches if necessary until shrimp reaches minimum internal temperature.
If using diced chicken, follow same instructions in Steps 1 and 4, stirring occasionally until chicken reaches minimum internal temperature, 5-7 minutes.