Why this works
Vinegar-to-vinegar swaps balance four things: acidity tier, color, sweetness, and aromatic profile. Acidity: white, distilled, white wine, champagne, red wine, and most rice vinegars sit in the standard ~5-7% acetic acid band and swap 1:1 by volume; sherry at ~7-8% drops to ~3/4 when replacing milder vinegar; balsamic and malt at ~4-5% bump to ~1 1/4. Color: balsamic, red wine, malt, sherry, and (lesser) apple cider tint pale dressings, beurre blancs, hollandaises, mayonnaise, and pale pickles; white/distilled/champagne/white wine and most rice vinegars stay pale. Sweetness: aged balsamic, IGP balsamic, seasoned rice, and (small degree) sherry carry residual sugars; subbing into a strict-sour recipe reads off unless the recipe's sugar drops, and subbing away means added sugar bumps. Aroma: malt for fish and chips, red wine/sherry for hearty vinaigrettes/gazpacho/romesco, apple cider for slaws/BBQ/biscuit acids, rice for Asian dressings/sushi rice, white/distilled for pickling brines/hot sauce/leavener roles. Verjus (~1-2% acid + residual sugar) cannot 1:1 a true vinegar without 2-3x volume or lemon backup; pickle brine is acid + salt + spices, so cut recipe salt and spices when it's the source and add separately when it's the target.
Where it fails
High in pale recipes (beurre blanc, hollandaise, mayo, vinaigrette, pale pickles, sushi rice, fish-and-chip service) with balsamic/red wine/sherry/malt/cider. High in strict-sour pickles/ferments with balsamic, seasoned rice, or aged sherry. Medium in baking-soda reactions with verjus or pickle brine. Medium in aromatic-identity dishes (malt on fish-and-chips, sherry on gazpacho, balsamic on Caprese) with neutral vinegar. Low within same color/sweetness family.