As far as the creation of physical objects in Reverie goes, this technique is normally referred to as dream weaving. Creating the objects in Reverie is generally considered fairly easy. Making them transportable to Evren is harder but doable as long as you are willing to accept that the objects are ultimately ephemeral. Dream weaving an object that would last indefinitely in Evren is likely nearly impossible. It should also be noted that actually creating physical objects is often considered wasteful by some weavers. These weavers would prefer to craft physical objects in Evren and craft power in Reverie, then pull the power from Reverie into Evren and imbue it into an existing physical object. This allows the weaver to focus on crafting the power the wish to imbue into the object rather than needing to concern themself with the physicality of the object (which can be easily duplicated in Evren).
It is also worth noting that there are creatures and items in Reverie that are “real” and are not constructs of someone's dreams or imagination. These things can generally travel to other realms just like creatures and objects of Evren can.