The taper is probably the most difficult thing to figure out for most runners. It’s time to rest but too much rest will leave you feeling flat on race day. I personally find this balancing act to be more difficult than the balancing act of pushing to my limit during the rest of my training without going over the edge.
As for speedwork or, for that matter, any running during the taper, its sole purpose once you are down to those final 10-14 days is to keep your legs loose and ready to go hard on race day. Really, the best taper for rest and recovery would be to not run a step during the final 10 days. However, that doesn’t work because our bodies “forget” what it’s like to run hard. So, to balance things out, we cut back the workload enough to promote rest and recovery without cutting back so much that our bodies “forget” too much.