Miro is a platform for remote collaboration using an online whiteboard. We used it for the creation of mind maps, user flows, wireframes and click models of an app. And for comments and discussions of the functional details on the ideation phase as well.
We used it for the creation of visual content and bitmap artifacts of our app. Having more "modern" tools for apps design does not cover the power of Photoshop.
Figma is an online service for interface development and prototyping with the ability to organize real-time collaboration. We used it for the creation of the mockups and prototypes, and for management of assets and mockups delivery to the Development team.