Which native american group is most likely to have a way of life similar to that of the mandans?

It is very likely that Sioux had similar way of life to the Mandans' way of life. In fact, they raised in the Great Plains, which leads to similar conditions. For example, both tribes lived in earth lodges, there are historical registers in which they fought in 1835, they suffered the smallpox epidemic in 1837, and for eating they developed the agriculture and both tribes hunted as well.

The Arikara are an Aboriginal tribe that speaks one of the Caddoan languages, They lived on the upper course of the Missouri River, between the Cheyenne River (South Dakota) and Fort Berthold (North Dakota). They currently share the Fort Berthold reservation with the Hidatsa and the Mandans, since these tribes shared the same custom and traditions.