If you have a choice use the thick variety since they need very little care while soaking. They remain soft and fluffy and retain the right amount of moisture needed for cooking the poha. The thin variety of beaten rice you use to make chivda or hachiid avalaikki. If using the thin beaten rice to make Kande pohe then add poha to a sieve. Pass the sieve under running water and add immediately to the tempering. Here it is not necessary for all the poha to soak it will be better if some of the poha is dry. This is extremely tricky so as far as possible I avoid it.