I repeat: Atheism is not essential for a particular worldview apart from the view that gods don't exist.
Atheism need not be essential to a particular worldview in order for atheism to have determinate characteristics. You can have a similar-looking garden without atheism, but that doesn't mean that atheism, when present, doesn't affect the garden. You're committing a subtle fallacy here. Just because I am allowed to substitute olive oil for butter in a certain recipe does not mean that butter has no determinate characteristics, or that it will taste the same.
While gods don't exist, religions do exist. It's quite possible to not accept the existence of the central character but still accept the teachings of a religion. As an example my worldview is probably different to that of an atheist in a predominantly Hindu country. This has a lot to do with the link between culture and religion.
What conclusion are you attempting to draw here? You seem to be leaning towards the idea that atheism doesn't matter because it doesn't affect anything.
To not believe in gods doesn't require a detailed knowledge of specific religions.
Of course it does, otherwise how would you know what you're not believing in?
Else we're hung up on words like "detailed." Granted, it is clear to me that many atheists really have no idea what they disbelieve, but without some notion or familiarity they would not even be capable of that blunder.
There is no reasonable proof of the existence of supernatural entities therefore there is no reason to assume any gods exist.
Since proofs terminate in conclusions rather than assumptions, I will assume you meant "conclude" rather than "assume." Easy mistake from a rhetorical hand.
But no, you're simply engaging in untenable
a priori reasoning. I would encourage you to be more empirical.

The only beliefs one is logically able to reject are those they have encountered in some form or another. There may be a species of aliens living in a distant corner of the universe who hold certain beliefs, but you are not able to disbelieve what they believe due to the fact that you have no exposure to the belief. You cannot disbelieve an idea that you do not know.
Even you reject the existence of all gods apart from your own favourite deity.
Silmarien answered this well.
I don't see either as speculative science. I do see it as rational to not assume a god exists in the absence of evidence.
No one assumes anything in the absence of evidence. That's just a truism.
Let's revisit your response to
proposition 1:
Of course there is going to be some connection between atheism and an individual's worldview. This doesn't mean that any two atheists will have a similar worldview apart from atheism.
A correlate of this is that there will be some similarity of worldview in light of atheism, and it makes perfect sense for atheists to argue about certain things in that vein.
Take an example. Two atheists grow up in the West and are cognizant of the common religious moorings of morality in the culture. In seeking to develop a working model of morality, one comes to believe that morality is objective and one that it is subjective. They naturally get into a discussion about whether atheism is compatible with an objective morality. They're not both right. Some options include:
- Their "atheisms" are different: they reject different concepts of God or religion
- They do not have common definitions of "morality," "subjective," or "objective"
- One of them has made a mistake about the nature of the implication between atheism and morality