It would only be shirk if you affirm there is someone in existence who is other than God and like him, in essence or attributes or acts. Non-dualism ( qualified and non-qualified ) does not assert this.
What about this universe ? There are two views. The simple answer is that this universe only exists as an illusion. But an illusion has no existence in reality once you know its reality.
You can say the claim that the universe is an illusion is wrong, but this claim doesn’t entail kufr or shirk. It would only be shirk if someone says this universe is God or that God is this universe, but no Sufis says this when they talk from the perspective of non-qualified non-dualism, where you don’t have any stages of descent. There is simply no universe, only God.
The confusion about the relation of the universe with God arises when you study qualified non-dualism where Sufis describe God’s self revelation in six descents (Hahoot, Yahoot, Lahoot, Jabroot, Malakoot, Nasoot) , where Nasoot is the universe itself. Here we need to be extremely careful. It’s important to not confuse being with essence. The realm of Nasoot is characterized by contingency and creation. It does not share the essence of God, his attributes and acts. The only aspect the universe has in common with God, relatively is BEING ( Wujud). But this isn’t controversial. All of you here believe God and the universe both exist or that they both are beings. The definition of being is to be found or experienced. IF you want to be on the safer side, you can add God’s being and the universe’s being are not alike since they are not found in the same manner.
As for me, l believe non-qualified non-dualism is correct. The six stages of descent don’t actually exist. The realm of Hahoot is the only reality. It is pure consciousness, bliss and being. Here God has no attributes or descriptions. There is no subject or object here. The Zikr for this stage is Huu in Sufism.