If you need it to be downloadable from the app store, then you will need to build it as a cordova app unfortunately, but simply doing this will not enable full offline support - this is a fairly large challenge, I posted here (as did others) with a skeleton of my current solution, Solution for Offline data auto sync in Meteor app. Similarly, you can attain full offline support for MOST scenarios, without cordova, even on iOS now they’ve enabled limited use of service workers.
Regarding the graphs on a phone screen, this is also probably nothing to do with cordova, do you have something similar to this in your <head>?
<meta name="viewport" content="viewport-fit=cover, width=device-width, height=device-height, initial-scale=1.0, maximum-scale=1.0, user-scalable=0" />