Thank you so much for the suggestions – I went with the longer straight stitch for the top-stitching and that seems to have worked great. I do have a lightening bolt stitch I used in other places, like the neckline seam.
Unfortunately, I got to the waist and despite my best efforts, it ended up very stretched out (I even got some of that clear elastic after reading another post on the issue)! I will take a breather then go back, take the seam out, and make another attempt – maybe stretching the elastic ever so slightly as I go. I knocked out a couple of pairs of the leggings in an effort for some instant gratification consolation. The leggings have worked wonderfully for me – 5 pairs (and counting) and they get lots of use – I will be swimming in little girls’ who wear leggings for years to come and am happy to be armed with a good go-to pattern 🙂