It is usually the events, layout, objects, memory usage or what's happening in the project, which is the culprit.
But anyway, exporters don't gain you performance. It's always the runtime. So, use the C3Runtime and improve your game design.
Here are some optimization tips:
About the exporter, it really is just mainly about the convenience and customizations you want to implement.
It wouldn't improve performance unless you use a custom webview, which is what Cocoon.IO does but has its own drawbacks and limitations. I don't recommend this, especially when Cocoon.IO is declining and performance is becoming worse instead of becoming better because of lack of updates while the regular webview and packaging improves.
I recommend, if you are not using the Construct 3 Build Service. You can use Phonegap. Which is convenient to use with its tools.
And no, it doesn't improve performance, that is up to the device webview, runtime and project design. Though, good, lightweight, updated packaging does improves a bit performance and responsiveness which is noticable.
And Phonegap is always up to date with this. And possibly the Construct 3 Build Service too.
If you learn or become an advanced user, you can use the Cordova CLI. But again, it doesn't improve performance. It works the same as Phonegap, it's just that you have more control.
The slight performance and responsiveness increase is up to the cordova packaging version but mostly on the project design and runtime.
I hope that shed some light on the subject.