Just in case you are in the mood to know about the Sri vaikuntam that is supposed to be three times the size of the material universe, पादोस्य विश्वा भूतानि त्रिपादस्यामृतं दिवि ॥ According to Sri Vaishnava faith, Iswara is Sriman Narayana and he has two eternal forms, dhivya Athma swaroopam and dhivya mangala vighraham. Both are supposed to be real and eternal and yet it is the Dhivya Managala Vighraham, also known as Subhasriyam, that is given lot more importance for it is this physical form that one is able to readily behold and serve. Among other things, it is the denial of this physical form by Sankaracharya that earned him the criticism of Prachanna Bouddha by Sri Vaishnavas.
Among the many works of Bhagavath Ramanuja is a collection of three poems in verse form collectively called Gadya Thraiyam. The three Gadyas are (i) Saranagathi Gadyam aka periya Gadyam, (ii) Sri Ranga Gadyam (aka sinna gadyam – many here I am sure have heard the beautiful rendition of this Gadyam by late MS), and (iii) Sri Vaikaunta Gadyam. In Sri Vaikunta Gadyam Bhagavat Ramanuja describes in vivid detail what it is like in Sri Vaikuntam, so much so, Dr. Radhakrishnan commented in his book on Indian Philosophy that the description reads like an eye witness account.
According to Visishtadvaitam, there are three eternals, namely, Chetana, Achetana, Iswara. Chetana is consciousness that is self aware, is atomic in size and possess a substance called Dharmabhootha Jnanam through which Chetana perceives the external world. Achetana is substance bereft of consciousness and Dharmabhootha Jnanam. Iswara is a Chetana, but Vibhu (all pervading), and is the cause of the manifestation of the universe.
There are three kinds of Achetana, namely,(i) matter of the material universe pervaded by the three gunas, (ii) suddha satvam, the self luminous matter present only in Sri Vaikuntam and (iii) time.
There are three kinds of Chetanas, namely, Nithya Soorees, Mukthas, and Baddas. Badda Jeevas are chetanas in samsara with accumulated karma over countless births. The only way they can achieve moksha (release) is by expending all the karma and that can be achieved only through Bhakthi Yoga which is the culmination of Karma/Jnana yoga. Those who have the knowledge, ability, caste based privilege for Vedic rites, and patience can follow Bhathi Yoga. Even if one of these requirements is unmet, then the Badda jIva can resort to Saranagathi in the prescribed fashion by which the Jiva beseeches Iswara to stand in place of Bhakthi Yoga and clear out all the karma thus leading to moksha. Such Jivas are called called prapannas who become Mukthas after reaching Sri Vaikunta. The third kind of Chetana is Nithyasoorees. They are jivas, but have never been in Samsara. Visvaksena and Garuda are examples of Nithyasoorees.
Iswara is Sriman Narayana. Some say Sri (Lakshmi) is also Iswara along with her husband and others say she is a Nithyasoory, but first among them.
When a prapanna dies he is escorted by Vishnu ganas through various parts of the material universe and finally reaches Viraja river. Here, the jiva takes a ritual bath and the sukshma sarira of the jIva is relinquished. On the other side of the river is Sri Vaikunta. There, the jIva takes on a body of any form to his liking, made of Sudda Satva.
Then he goes to the mani maNdapam and sits on the bed of Sriman Narayana and Lakshmi and proclaims aham Brhmmasmi, i.e. the soul of my soul is Brhmman and my soul is Brhmman’s body. Then, he joins the congregation of Mukthas and Nithyasoorees and serves Sriman Narayana at the command of Sri conveyed through Visvaksenar.
The muktha like nithyasoory gets the ability to take any kind of body in order to serve Iswara in any manner whatsoever. Serving Sriman Narayana bestows the jIva with incomparable and uninterrupted bliss that is equal to that enjoyed by Sriman narayana himself.
The masculine pronoun “he” used above in reference to jeeva is misleading as jeevas are free of gender and gender is only to the body according to Visishtadvatam. In Sri Vaikuntam Mukthas and Nithyasoorees are free to take any body, male or female, in the service of Iswara.
The above is mainly based on what I have gathered from several sources, mainly from the Tamil commentary to Swami Sri Desikan’s magnum opus Srimath Rahasya Thraiya Saram called Rahasya Thraiya Sara Vivaranam written by the present Srimath Azagiya Singar of Sri Ahobila Matam. Any errors in my account are mine alone, not that of Srimath Azagiya Singar or Swami Sri Desikan.
Let me further add, I have no personal belief in any of this.