Let’s settle this debate here. Which one will you prefer for the Mid-Size React JS Project?

Mantine

Using antd for the first time for a side project, finding it to be pretty good.

Where was the debate in the first place? Anyway, if this is a company wide project with more than a few developers working on, then Tailwind is better. Only one or two then Bootstrap.
Big product based companies usually have their own custom libraries for their products

Css modules

SCSS along with BEM Convention :)