Lets say I have animated assets of different models with many different accessories. I'm using this all assets in point instancer as references, and after instancing is done I'm randomizing time offset on instances. Now I'd like to randomly hide different accessories on different model variants. Is it possible on this stage of scene assembly?

You need to create a prototype for each variation you want to use as a prototype. The Edit Prototypes LOP can be helpful for this.

edit prototype seems handy in this case. For now I've used explore variants and after that randomly instanced them, and it worked fine. Thanks for suggestion