Personally I would just use the Miso but add it like I said at the end when all the veggies are cooked. I looooove Miso for the taste and it is also a super nutritional addition that is also a probiotic. Do a little research on it. It's wonderful stuff and a great addition to a healthy diet.
I rarely use the white miso cause I like the stronger tasting darker stuff. The lighter Miso I believe they use rice with the soybeans. The darker or Mugi Miso that I like they use Barley. In traditional Japanese cooking if I remember correctly the light miso is used more in warmer weather and the darker miso in the winter.
I make a great winter dark miso soup with butternut squash, fresh corn and wakame seaweed that will raise the dead ;+D. I haven't made it in eons and now all this Miso and soup talk got me thinking about it. Dunno if butternut squash and corn are available right now but I'm gonna check the store tomorrow and make some if they have it.