There is no right answer to these questions. My "educated" preference these days is always Figma plus task management tool like Asana or Jira.
TL; DR version of the advantages of FigmaEqual to or better than Sketch, but available on all platforms and browsers, InVision replaces Prototyping and Comments, as well as Zeplin, because you can embed developers in Figma and download the latest version of everything they need.
* Long versions
Design System Manager
I think Figma is pretty well equipped to design and maintain a design system. You can define font styles and color scheme, and the component system and IMO implementation are much more powerful than Sketch's.
Figma's prototyping has improved in the last 2 years and is now comparable to InVision. They can easily emulate floating states, sticky elements, vertical and horizontal scrolling, and so on.
You can design responsive, scalable components, but in reality, you still need to have at least 2 versions of the layout, and in many cases, 2 versions of each component. If you want HTML / CSS-like flexibility, you must design in HTML and CSS.
"In a nutshell" comments and answers are not particularly exciting. They are identical to InVision and Marvel, but if you have them directly in the tool, you can shorten the iteration time.
A single source of truth
Unlike file-based sketches, Figma files are hosted in the cloud and live-updated: no file versions and conflicts. That's huge, if more than one designer is in the team. It hurts to try syncing sketch files at the end of the day. If necessary, the Figma file can be taken offline.
Developer transfer eliminates the need to use Zeplin or wait for the designer to extract assets.
Components and libraries
Components are similar to Sketch's icons, but I think that Figma's implementation is much better because it gives more control over what you can override in instances (not just scaling, text, and internal symbols). In this sense, the Figma implantation is closer to the OOP classes and instances. Add libraries to the mix, and you have the perfect tool for creating design libraries.
I've built my design process to have all the design in Figma, plus a thin layer of "Definition of Done" and related links in Jira or Asana Ticket.