if your planning on moving them outside into the ground i reccomend choosing tall containers so that the plant grows deep roots and then when you put it into the ground those roots will go deeper and be able to get groundwater faster..
for indoor i would say start them in a smallish party cup siza container, let it get rootbound before you transplant into a bigger container and when you do break up the roots a bit so they will grow outwards (if need be, depending on how root bound it is) being rootbound is a good thing it means your plant will grow faster and be able to use more water, up to a certain point when it is completley root bound then it slows growth... who ever said start in your max size container is wrong... when the plant grows the roots reach out the side of the container and to the bottom thats why your seeing roots at the bottom, if you do start with your max size container and dont start with a smaller one you risk not getting as good of a root system as you could have if you did what i mentioned..
as for the exact size you should choose... its all up to you, the bigger the pot the bigger the plant will be and the more water it will need indoors, you need to figure out what space you have yo work with and how many plants