I founded one of the first independent app development studios just as App Store went live in 2008. In addition to building this successful indie studio, I've helped dozens of companies launch successful apps on App Store and Play Store.
Given your requirement, you will need to look for an architect who is familiar with the technologies you've listed in the question, AND a development environment that will support those technologies.
There are several frameworks, languages and stacks you can use to code and deploy and deploy mobile apps. If you intend to deploy to both App Store and Play Store, the idea of developing once and deploying to both is appealing and there are many options to do that. Frameworks like Appcelerator, React Native and Xamarin are used by major brands for their iOS and Android app development.
On the other hand, many well known brands have tried that approach only to backtrack and re-code in the native language and development environments (Android Studio and Java for Android, xCode and Swift/Objective C for iOS).
The frameworks will never be as robust and open as the native environments provided by Android and Apple but they will allow you to develop less expensively since you can code once and deploy to both.
It seems that you initially need for someone that has a broad knowledge of environments to help you make the best development decisions up front that will support your technical requirements. I see a danger in selecting someone who is committed to a specific development framework rather than considering the best one for your requirement.
I hope this give you some idea of what you're looking for. Please give me a call if you want to talk this through.
