tablets

You need to work out what you need it to do and where. Chromebook isn't much fun if it isn't connected to Wifi.

I quite like having a toy 10.1" ASUS T-100 which will work as a tablet or a tiny laptop for emails on the road and travelling light. The 17" workhorse is a bit of a drag for the odd email even if it is powerful. Mine has Win 8.1 on it but now they come with Win10.

I originally bought it for the inclusive Office 2013 license deal.

Be aware that I don't have a chromebook nor does my daughter, and my anecdote is worth what you paid for it!

It does illustrate that, as is often the case, answering questions is much easier than knowing which are the touchstone questions.

Chromebooks do EVERYTHING inside the Chrome web browser. Everything you install from the Chrome Store (apps, games, utils, etc) are either extensions or addons to the Chrome browser. Even system configuration is mostly done from the Chrome browser. If the application you want to run does NOT require internet access, it will run offline. She can read a book, create documents, deal with local email, and play games. She cannot surf the web, send and receive email, or run web apps, but everything else works.

Google is aware of the problem of using a Chromebook offline and has done what it can to make it usable:

The Chrome web store has a section specifically for offline apps: Not the "Runs Offline" button on the left.

Also, I don't ride the train very often, but many passenger trains have wi-fi: