Lakshmi,Sita and spouses of Krishna. What is their position according to Srivaishnavites,Gaudiyas et al? Are they also supreme or are they subservient to the supreme deity?
In Gaudiya Vaishnavisim Lakshmi is not a Jiva and is non different from Sri Vishnu.
In Madhava Sampradaya she is said to be a Jiva (hence subservient to Sri Vishnu). But she and Durga are beyond Samsara.
There are two sects in Sri Vaishnavism - Vadakalai and Thenkalai. Vadakalaites do not consider as a Jiva(hence equal to Sri Vishnu) But Thenkalites do say that she is a Jiva, but not an ordinary one as she is a Nitya Siddha. Hence she is subordinate to Vishnu but beyond Samsara etc.
Source: Hari Das's answer in Quora
If Supreme Lord is the all powerful (shaktimaan), His eternal consort is His internal potency (antaranga shakti). Without antaranga shakti, shaktimaan Lord is incomplete. Thus His eternal consort is not subservient, rather to be accepted as Their servant of the servants is the ultimate goal of our life.