The cabled bind-off is what really sets this shawl apart. The body of the shawl is soothing knitting that is so easy to memorize.
The yarn used is a 100% Merino fingering weight by Miss Babs but any fingering weight yarn will do. There is no reason you couldn't use leftovers as the variegated paired with one solid skein. I used ~25 grams of yarn for the bind-off by my testers are using between 16-25. If you are looking to make the shawl larger you could use all 400 of your variegated color and then have ~500 yards of the solid. That extra 100 yards should be enough for you to do the edging.
The style of this shawl makes it so that the stitch count isn't important at all except for keeping the shape of the shawl. I hope you have so much fun with Henness! Can't wait to see your combos, if you need inspiration you can check out the test knitters projects here!