Do the atheist extraterrestrial Anunnaki, Arcturians, and Reptilians have guardian angels to protect them and do they have additional angelic support like humans, or does their lack of belief limit this?

They are without divine support at this time. This has happened through their own choosing, in effect, by leading lives of depravity and immoral conduct, through exploiting others, and causing enormous harm and suffering to all they encounter. This is an example of the slippery slope made possible through free will when one becomes too selfish and self-serving, with no regard for others, and becomes so corrupt they lose the ability to love, they erode their connection to the divine, and the divine realm is further and further distanced and unable to help them. This is what led to the fallen angelics being cut off from divine assistance. Their contamination of the physical extraterrestrials in your realm has sent them on a similar path. Their corruption has dragged them down to the point where there is less and less divine realm can do for them. They still have the benefit of life support, but not much beyond that, unless there is a momentary easing or change of heart which may receive divine amplification to reward a positive impulse, but this happens less and less. They are on a path to oblivion, and this is a cautionary tale for human as well, given their high level of corruption.