When it comes to Layer 2, the impression I have is that Uniswap is working on a solution in line with Optimistic RollUps.
Key advantages of this Layer 2 method being the below
They built a project late in 2019 with https://optimism.io/ called ‘UniPig’ that was a proof of concept for this Layer 2 scaling method.
Other projects are using other methods, when I was researching this I saw Loopring’s exchange as a concern. They use zkRollups
DiversiFi, is another exchange like Looprings, except it works with an order book, that I was interested in, it uses Starkware’s implementation of Zero-Knowledge RollUps.
I think the main benefit of Optimism is the ease with which the developer ecosystem can port over projects to an ‘Optimistic’ side-chain, without having to learn a great deal about new technologies or languages. Someone with more knowledge will need to chime in if you’re wanting a clear and reliable understanding.