My main doubt is Windows x Chromebook. What I'm looking is for a light and thin device with good battery life and only task is doing the basics like writing and editing text and light web browsing. I know chromebook would be the obvious choice, but I'm insecure about using Google Docs instead or Word, since I need to do very detailed editing in my texts. But i really like the idea of paying 200$ for a laptop... 

Just pick up the cheapest laptop you can find. Literally anything would do the trick with those requirements. I mean, here's a link for a whole category of laptops between $100 and $200 with the bare minimum specs that would suit you fine: http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&IsNodeId=1&N=100006740%204017

Don't get a 200 dollar windows. That's basically asking for constant lag

just go to a Bestbuy(or any good electronics store) and ask for the best Chrome book. Chrome books are cheap but great due to their decent performance and overall stability

Buy a Macbook