The question arises in my mind when considering theism and atheism is the various strands of Realisation of the truth:
Consciousness-advaita, Brahmo-advaita, Vishista-advaita, Shudha-advaita and now Satya-advaita: take your pick, or is yours Dwaita?
I have used the term Brahmo-advaita for classical Advaita Vedanta according to the scriptures enunciated by Sankaracharya in 'Brahma-satya jagat mithya'so that Brahman is the only Reality and the phenomenal world is Maya that is apparent and hence illusory. This makes the philosophy God-less so atheistic.
Buddhism is a distinct variant of Brahmo-advaita focussing on alleviation of the human sufferring condition through Dhamma in the vow taken by adherents to observe the 4 Noble truths and the Eight Fold path to attain nirvana or liberation from the phenomenal world that it considers real The reason that I have placed it here is thst it discusses the impermsnence of Reality but is widely accepted as being atheistic (could a benevolent God have created such a terrible samsara that people would wish to escape from it) even though some would argue that this was God's purpose . So it is contentious that the Buddha was personally non commital on this specific point.
Shudha-advaita is union with God as a Personal Higher Entity such that everything is this God and living beings are living Gods. It is purely theistic.
Consciousness-advaita isays that Consciousness e source of everything and is everything as a single Entity that an advatist is in union with no Creator or Personal gods. It is atheistic The philosophy is encapsulated in the term Satchitananda, that is translated as truth-consciousness-bliss.
VIshista-advaita is theistic based on achintya bhed abheds tatwa of oneness and separateness with Supreme God Sri Krishna/Devi Durga existing in the Reallty of Brahma-Nature with millions of guna consciousness gods and goddesses representing different blends of sattvic, rajasic and tamasic attributes. It is qulified monism.because it has a material dimension of reality (vyvaharika) in ehich a prrsonal God is experienced and a spiritual dimension of reality in which through loss of attachments anf bondages the Self is realised for total liberation of operation. There is no scientific proof for any of it so it counts as a philosophy. There are different dharma for vyvaharika (dharmayudha) and paramarthika (conservation, preservation and harmony in Brahma-Nature). There is continual bhakti for God with surrender only in vyavaharika. The conceptul8sation always remains a faith that accepts the preordination and preorchestration of the universe in s Grand Design such that living beings have fates/destinies/kismat and yet have their own freewill to change their circumstances.
Satya-advaita is agnostic atheotheism in keeping an open mind that both Creator God and Personal God may exist but the practitioner has not had concrete proof of these as highr entity or power. The advaitist is at oness with truth at all tiimes so without scientifically justied proof that he/she continually sarches for a conception of Reality is not yet formed incorporatin invisiblible and undetectable elements. Pending such a formulation words like Brahman and Brahma-Nature are not in the vocabulary. Only Nature is known as Reality for certain based on energy-mass equivalence of E=mc2. There are no specific duties and duties other than living in truth and in the reality of the moment. The satya-advaitist therefor has no aims objectives, wishes, plans, aspirations, hopes, anticipations, expectations desires or ego as he/she awaits the truth to get revealed into his/her thoughts every moment in patient mental explorative mode of operation. There is acceptance of a higher Self as a state of ones true nature free of attachments and bondages of the mind so that the practitioner is totally free to live as living in truth comes forth. He or she has faith in truth alone (satryamev jayate, that is to say truth is sacrosanct and must be allowed to prevail).
Dwaita is theistic in which God is the controller of the universe in having created it and also preserving it. People pray to God as their Saviour in life. God is known to different established religions by names such as Allah, Jagannath, Krishna, Yahwey, Jehovah, and Ram. Holy Books have been written since the year 3000 for people to follow the comandments of their particular God such as Bhagavad Gita for Hindus, Torah for Jews, Koran for Muslims and Bible for Christians. People follw these and either love God, or fear God.