Iyers denoted only they belong to so called highest jaati of brahmana varna ,
Smartha got added to it at adi sankaracharya time.
Smartha meant only follower of smriti
They worshipped easwara made up of five manifestation incuding siva.
Later smartha bacame synonymous with worship of siva
Many who became followers of Ramanuja got called as iyengars.
In that sense could be called off shoot of iyers and are vaishnavite iyers.
Other iyers became smartha iyers meaning followers off siva.
Smartha got added to it at adi sankaracharya time.
Smartha meant only follower of smriti
They worshipped easwara made up of five manifestation incuding siva.
Later smartha bacame synonymous with worship of siva
Many who became followers of Ramanuja got called as iyengars.
In that sense could be called off shoot of iyers and are vaishnavite iyers.
Other iyers became smartha iyers meaning followers off siva.