Snort and Amethyst directly show you when you enter someone's profile if they follow you or not. Primal sends notifications for new followers.

You can use Amethyst, Snort and Plebstr to manually check your Follows and Followers lists. And Coracle to check your Followers list ( I like it because it loads the profiles of people sharing no relay wih you much faster than the others, but Idk why it doesn't load the Follows list )