Thanks for getting back to me! I made changes to a components for my signin screen. I also updated the app.json to include splash and update properties.
Changes to your splash screen will require submitting a new IPA and APK to the stores because the splash screen is embedded in the native apps. You should be able to deploy JS changes more easily, though. In particular, the new Updates API in SDK 26 lets you more finely control the policy for getting JS updates.