Whether the culture is good or bad is not strongly indicated by the size. You’ll get a good feel by meeting them. Prepare some questions on turnover and overtime use. You want both low.

You will have to do work that in a bigger company would be specialist work. Some possible examples: Maintain infrastructure, drag network cables, purchase your computer, negotiate with service providers, software architecture, UX, product strategy, frontend, backend, integrations, customer support, QA, etc. All this could be heaven or hell based on your personality. :)