Shapewear should feel snug and supportive, not restrictive. The most common mistake is sizing down for "extra" compression, which usually creates more visible lines and less comfort, not less.
You should be able to sit down, breathe normally, and raise your arms without the garment rolling, digging, or cutting off circulation. A well-fitted piece smooths the silhouette through even, distributed pressure — it should not feel like a single tight band anywhere on the body.
If a medium-compression piece in your size feels too tight, try the same compression level in the next size up before jumping to a lighter compression level — sizing correctly usually preserves more of the smoothing effect than reducing compression does. Only move to a lighter compression level if the correct size in medium still feels restrictive for your comfort over several hours.
See the full bridal shapewear guide for compression levels and garment types, and the sizing and fit guide for how to measure accurately before you buy.