The difference is logical coherency. The 'all roads lead to Tengri' argument is based on a fallacy. https://en.wikipedia.org/wiki/Equivocation

Whereas the perfect God argument is based on the premise that a God exists.

If the premise is that Tengri exists, shouldn't the all religions argument also work for Tengriism?

If Tengri is God, the Tengriist make additional claims about his nature. You need to follow up with additional arguments.

An omnipotent god would be a perfect god, logically

Correct.

Tengriists believe their god is omnipotent

Good so far.

And that their god provides different methods to reach him

So if god is perfect

Then this last statement must be true

That's the unknown quantity. How does a perfect God act his goodness?

I've been looking for servers like this for a year

Tengriists believe their god is perfect I presume

Which is why they justify everyone going to paradise

Why would everyone have to go to paradise?

I believe Tengriists follow the philosophy of determinism

The Tengriist believes in a god without standards.

Which is the reason they use the different paths for different cultures argument

But why does a perfect God have to deliver everyone to paradise?

Why does god necessarily need standards?

Why does a perfect god not délivrer everyone to heaven?

The Absolute, be definition, is beyond us. We are like children asking why we can't all have candy all the time.

Of course, I don't agree with any of this nonsense

I am simply making my case that the two religions are similar

This is a theoretical argument, sure.

In their fallacious logic

The both have problems, but for different reasons.

I am pedantic about why things are wrong, not just that they are.

My logic is that if we can make the case that two logics can be disproven on the backbone of similar logical failures, then one cannot reasonably choose one over the other

Religions*

It would then be illogical to pick one religion over the other

There can only be one primarily correct religion, but it is possible that some religions can co-exist as a subset of another.

Tengri is one example, Islam may be another grey area.

The issue is that in this case Tengriism and Christianity clearly contradict

They do.

From the perspective of Christians