Cosmos is a really new lib, so when we did our initial research it wasn't even out yet. You can read more about our research over here: https://memgraph.com/blog/you-want-a-fast-easy-to-use-and-po...
From what we've understood, it's somewhat limited when it comes to graph styling. But an amazing technology nontheless.
Actually that was the main reason (along with the note that main authors are not contributing to visjs any more [1]) for a creation of the Orb where we fixed the blocking UI issue with graph simulation. Orb engine has two parts now:
* Simulator that doesn't depend on the DOM so we can move its heavy calculation to the web worker - we use d3-force for it [2]
* Renderer is pretty much influenced by vis-network, using similar style mechanism and canvas drawing capabilities (we credited vis-network in our code for those sections)
[1] https://github.com/almende/vis/issues/4259#issue-412107497
Happy that people are building new graph visualisation engines and I think still a very open space for innovation in interactively exploring graph/network structures.