Ask HN: Database for collecting research data in rural areas

I'm designing an offline-first web apps that allows researchers to collect research data on-site in rural areas. The current requirements is that they would go out to areas with no electricity and fill out forms on their mobile devices. I choose mobile devices rather than laptop because everyone has it and with power banks, one can easily extend the battery.

At the end of the day, they would run return to hotel and sync the data with a remote or local server. I did my research and it seems like these are promising solutions:

- PouchDB (https://pouchdb.com/) - Gun.js (https://gun.eco) - Roll my own

Do you have any experiences regarding this?