Philosophy: Do Christian saints go to the spiritual world?

can they go to goloka vrindavan, vaikuntha or just brahmaloka?

Big subject and another possible 'jiva issue' since Prabhupada said several things: heaven (Svargaloka), Brahmaloka (Satyaloka), Vaikuntha.

"Similarly, in the Christian world, the Bible is worshiped. It is a
fact that the Lord Jesus Christ is present by His words. Krishna is
also present by His words. These personalities, either God or the son
of God, who come from the transcendental world, keep their
transcendental identities without being contaminated by the material
world." (Krishna, The Reservoir of Pleasure)

Bhaktijana: Does Jesus Christ reside in the Vaikunthas or Brahmaloka?
Prabhupada: No, Vaikuntha. He's person. Brahmaloka, Brahmaloka is
within this material world, and Vaikuntha, in the spiritual world.
(Boston Dec 23, 1969)

But is there more than Vaikuntha?

Once I asked a Catholic theologian what does their theology say about the Paradise. He said there is no consensus. Actually, there are only three mentions of it in the whole Bible - Luke 23:43 (Jesus promises to take there a crucified criminal who spoke on His behalf), 2 Cor. 12:4 (there are things beyond human expression), and Rev. 2:7 (there is a tree of life).

The word Paradise comes from Avestan pairidaeza and Sanskrit para-desha, lit. the supreme country. God's own realm of Gokula (in Japanese Amida Buddhism Gokura-ku).

If you look at Fra Angelico's 'Last Judgement' painting (link below), you'll see Paradise pictured there on the left. There is a tree of life (and another tree) and a circle dance of liberated souls. In the middle is a hole. In Muslim art it similarly indicates the presence of the Prophet or divine beings. It visually says, 'Those here cannot be depicted.' In other words, the plants and hole indicate a divine presence, which is considered too sacred to depict.

http://www.wga.hu/frames-e.html?/html/a/angelico/03/index.html

Vaishnavas immediately recognize Lord's rasa lila, His most confidential pastime. In the middle are missing Sri Sri Radha-Krishna. This circle dance is known also from other traditions though (Helios and Rhoda, Apollo, etc.).