Pick your use-case first: cold dressing/dip needs an emulsified, spoonable texture; baking needs richness with stable tang.
Choose the closest match from the table, starting with Japanese mayonnaise or full-fat mayo + rice vinegar for the most Kewpie-like bite.
If your substitute tastes flatter, add acid in small increments (rice vinegar or lemon juice) until the tang matches your dish.
If your substitute is too thick or breaks (especially yogurt-based swaps), thin with a teaspoon of water or milk and stir/blend until smooth.
Taste and adjust seasoning at the end; for sweet-salty Kewpie-style flavor, a tiny pinch of salt usually restores balance.