ANSWERED: wahdatul wujood

Salam, i really did not want to ask this, but i have to. I am told that it is haram to believe in this concept and those who completely believe that Allah (swt) is in his creation are mushrik. But then at the same time many ulema have upheld the notion of wahdatul wujood - but on what basis can they hold this up, and also one can ask why bring such an issue into aqeedah because it is not something which is found in the times of the salaf or in places like Aqida Thahawiyyah? Also, are there different variants of this?