I've been working on a virtual table (not for React, but KnockoutJS) that's designed around needed to virtual scroll over a large number of columns (as well as rows). Really in-progress code at the moment, but getting there...
You can edit that on JsBin and easily increase the columns to 5-10,000. You may want to look at [editableCell](https://github.com/gnab/editableCell) for some of the keyboard shortcuts.
[Knockout-Virtual-Grid](https://github.com/jstclair/knockout-virtual-grid)
[Live Demo](http://jsbin.com/roheqo/1/)
You can edit that on JsBin and easily increase the columns to 5-10,000. You may want to look at [editableCell](https://github.com/gnab/editableCell) for some of the keyboard shortcuts.