I've only ever tried the medium. I didn't think to ask if other widths were available, though at the price, it's very doable. I did try one of the clear ones not too long ago and though color or opacity/transparency shouldn't matter, it did feel different somehow. I don't know if I liked it or not.

I wonder if there are subtle creative benefits to using "your favorite ____" while working.

I certainly think there are. I have no hard evidence, but when writing with a pen and particularly a fountain pen, sometimes I'll write something just because I enjoy the feeling of the nib on paper traveling through the pen and into my hand. Sometimes with typewriters I do the same, but because I like the sound, or the way I have to engage with it much more physically. On a computer I have noticed that I chop things up and move them around in ways that I can't otherwise and sometimes good things have come out of that.

Or if it constrains you within things created by it in the past. Or if it doesn't matter whatsoever.

This is really interesting to think about and it hadn't occurred to me before. I have often wondered what it might be like to use the implements of someone I admire. I'd like to check this out someday, though I can't imagine what circumstances would have to conspire to make that a possibility, much less an opportunity.