Ethereum L3s and app chains provider similar types of experiences.

Applications specific chains need tight interoperability with other ecosystems. The best examples of app chains are spot and perp dexes.

Interoperability enables accessing data from inside those chains for liquidity onboarding, oracles, liquidity rewards and other ways in which markets interact with broader ecosystems.

Two things end up mattering a lot.

1. Topology matters. A app chain builder needs to understand the topology users and ecosystem apps will need to traverse. Where you have high quality connectivity you limits capital, onboarding and other parameters.
2. Developer experience matters. The more infrastructure you have to build and maintain as developer then the harder it will be to builder and attract an ecosystem.

I might be missing things here but the L3 storage proofs ecosystem seems nascent from both a topology and developer ecosystem pov.

I would be concerned with solutions that lock L3 builders into topologies clustered around an L2. Cosmos chose to make the topology very ad hoc. Creates a lot of drama but ultimately the best solution to attract builders and give them many options to onboard liquidity.

All we’ve learned from the builders on top of IBC is that an extensive world of testing, simulation, middleware, relayers is required for building interop solutions work. IBC and CCIP have seen the deepest developer experience