In Newer Super Mario Bros. Wii
In Newer Super Mario Bros. Wii, they behave the same as in New Super Mario Bros. Wii, the number of Mushrooms that appear out of blocks depends on the number of players there are, as well as their current forms, as one will appear for every Small or Mini player currently active. However, with two to four players, if every person does not have a power-up (excluding Mini form), one higher class power-up (such as a Fire Flower) will appear.
In Newer Super Mario Bros. DS
They behave the same as in New Super Mario Bros., they don't replace higher-tiered power-ups in the Item Storage (like the Fire Flower), giving 1000 points instead.