It totally agrees with the idea that Nano and Microinfluencers usually give better results than great celebrities. I have also proven it in own campaigns: the closeness and authenticity they transmit makes the audience trust its recommendations more. To choose the right ones, the first thing I do is analyze the coherence between its content and the brand values. It is of no use that have thousands of followers if they talk about issues that are not related to the product or service that I want to position.
Another key aspect is to review the quality of the interaction. I do not look only at the amount of likes, but in the comments: are they real, show genuine interest or see generic? That says a lot about whether they really have a solid community or simply passive followers.