11gb is taken up by the OS, so you only have 53gb free, but that's plenty for most games.
There are a few games with installs of several gb, but not many, though I imagine that will increase over time.
If you're not planning to put movies on it and use mainly for PCVR then I'd say 64gb is enough. I went for the 256gb mainly because I plan on putting movies on it, and with the hi-res screen I can now put higher quality encodes on there, which will take up large amounts of space.
I can imagine movies taking up a lot of space, but I can stream them from a dlna server if needed. I'll stick with the 64gb for now, thanks.