According to Shia Islam God does not always do works himself directly and do them using angels and also prophet and Ahl Bayt as servants and intermediates between God and Nature. But this does not mean they have any independent power or decision. But this will of God that some works be done using "tools".
For example about collecting the soul ( توفي) at death there are 3 different verses:
One verse says angels take the soul at death.
Another verse says the angel of death takes the soul at death.
Another verse says Allah himself directly takes the soul at death.
فَكَيْفَ إِذَا تَوَفَّتْهُمُ الْمَلَائِكَةُ يَضْرِبُونَ وُجُوهَهُمْ
[47:27] Then how [will it be] when the angels take them in death,
striking their faces and their backs?
اللَّـهُ يَتَوَفَّى الْأَنفُسَ حِينَ مَوْتِهَا وَالَّتِي لَمْ تَمُتْ
فِي مَنَامِهَا ۖ فَيُمْسِكُ الَّتِي قَضَىٰ عَلَيْهَا الْمَوْتَ
وَيُرْسِلُ الْأُخْرَىٰ إِلَىٰ أَجَلٍ مُّسَمًّى ۚ إِنَّ فِي ذَٰلِكَ
لَآيَاتٍ لِّقَوْمٍ يَتَفَكَّرُونَ
[39:42] Allah takes the souls at the time of their death, and those
that do not die [He takes] during their sleep. Then He keeps those for
which He has decreed death and releases the others for a specified
term. Indeed in that are signs for a people who give thought.
قُلْ يَتَوَفَّاكُم مَّلَكُ الْمَوْتِ الَّذِي وُكِّلَ بِكُمْ ثُمَّ
إِلَىٰ رَبِّكُمْ تُرْجَعُونَ
[32:11] Say, "The angel of death will take you who has been entrusted
with you. Then to your Lord you will be returned."
But which are true? Finally who takes the soul?
to solve the problem it depends on the tank of one who dies. Because death is in fact enter in the universe (Barzakh) it is like when someone enters a new country. If this one is a usual person so the employees check his visa and he enter. if he is an important person may the foreign affairs minister welcome him and if this person is VIP like a president the president of new country directly welcomes him.
Similarly if the Muslim is a high rank believer God himself directly takes his soul and if lowe rank the angel of death who is boss of many other angels take his soul and if it is a normal person normal angels take his soul.
According to Shia Islam Ahl Bayt (including prophet) are intermediates for delivering mercy of God to human and Nature and they have also control over the nature by will of God and if they want they can do miracle by controlling Nature.
But consider all of such powers is granted to them by will of God.
For another example Quran says:
ثُمَّ إِنَّ عَلَيْنَا حِسَابَهُم
Then indeed, upon Us is their account. [88:26]
This verse is about Judgement at Judgement day. Who are "We"?
There is a Ziarat said by Ahl Bayt to Muslims to recite it whenever they want to meet prophet and Ahl Bayt either at their graves or at any place reminding meeting their soul to achieve very high reward by God and acceptance of prayers and asking (dua) from God. Because this Ziarat is said by Ahl Bayt is considered same as Hadith and is considered to be truth because it is derived from divine knowledge of Ahl Bayt. In this Ziarat some of the works that God has decided to be done by prophet and Ahl Bayt are mentioned and one of them is Judging Muslims at judgement day:
So finally "we" sometimes means God and angels and sometimes means God and prophet and
(This Ziarat* awarded by the tenth holy Imam of the Shi'ites Hadrat Imam Ali an-Naqi (A.S.) to Musa ibne Abdullah Nakhee at his request to teach him a comprehensive way of paying homage to any of the infallible Imams during pilgrimage in their shrines or from far away places is an excellent lesson on Imamat by the Imam himself.
Whoever recites this ziarat with love and cognizance of the divinely appointed Imams is purified from diseases of soul and body and all worries if the Imam intercedes for him. A pilgrim, who obeys the Imam, refrains from all sins and all of his good deeds which lack in perfection are accepted by Allah.
First recite the 'Kalima', then Takbir 100 times, then recite as follows)