1. I used firm tofu called momen-dofu as I like its flavour better than silken tofu and it is easier to handle. Silken tofu is also fine but be careful not to break the cubes as they are very soft. Eextra firm tofu does not suit a delicate soup like this. The quantity of tofu is also flexible. If you like tofu, increase the amount. The same applies to quantity of wakame.
2. Depending on the type of miso and the brand within the same type of miso, saltiness varies. So you might have to adjust the amount of miso to add to the dashi. I used awase-miso in this recipe.
If you have miso which already contains dashi, you can use water instead of dashi stock. However, I think that the dashi flavour mixed in the miso is not as strong as it should be. You might still have to add some dashi to the water.
3. If you don’t have an appropriate sieve to use, place the miso paste in a small bowl, add some dashi to it and dissolve the miso in it. Then pour the miso mix back into the pot. It is important not to just drop the paste into the pot as is, because (1) it will take a while to dissolve, (2) in trying to dissolve the miso, you will probably break delicate ingredients like tofu.
4. Unlike other vegetables, tofu and wakame do not have to be cooked very long. In addition, tofu is very delicate, hence miso soup is made before adding ingredients. The same method should be used when making miso with beaten eggs which is listed in Miso Soup Ingredients Suggestions.