How do I choose the right size in women's shapewear?

I visited a clothing store two days ago to find shapewear for daily use. I wanted something that felt supportive and comfortable under outfits without being too tight. But when I checked the options I felt disappointed. Some pieces felt too tight even in larger sizes. Some did not give clear compression levels. Some felt uncomfortable after just a short try on. I could not trust them. I could not decide confidently.

Then I visited another shop in the same area. Some shapewear looked better but sizing still felt confusing. Some items felt supportive but too restrictive for long wear. Some looked fine at first but did not match body comfort expectations. I remembered once buying shapewear that looked right but felt completely wrong when worn for a full day.

To check more variety and options while scrolling many online marketplaces including alibaba I found many shapewear options with detailed size charts. Some explained compression levels clearly. Some included body measurement guides. Some had customer reviews mentioning real fit experience. There were many options available. This made me interested but still unsure again.

Now I am thinking is it better to size down for shaping effect or choose true size for daily comfort?