from my understanding, the tubes clip almost the same in low voltage as they do in high voltage. The major difference is that at low voltage, they tend to distort easier/earlier (which is a good thing if you are building a distortion pedal!). The major difference is the headroom between a starved plate and the high voltage one.
Someone please correct me, but, from my understanding, the more headroom, the more nuances you can get in tone / distortion.
Anyways, if you want to see a fairly simple tube distortion with starved tube, go see:http://www.geocities.com/slajeunesse/ruby_tuby.html
What you are looking for is the first part right before it gets to the LM386.
Another interesting thing that might be worth while to investigate, instead of using an opamp to drive the tube section, try using the fetzer valve circtui from runoffgroove!!! This could prove to be a kickass combination!