Architecture option needed

I am building an app which will be used on Android, iOS and the web browser.

It needs to scale to about 3000 concurrent users, and should enable easy content addition and dashboards if needed. It should also be offline. These users will generate posts, images and such content.

My options are 1. Native Android, iOS and web 2. React native or ionic 3. Responsive web

With limited support of pwa in iOS, that option is out. With limited caching of data, I feel web browser or responsive is out. I tried ionic, but found it quite troublesome.

Please suggest between native and react native.