You don't really give enough info here about which bulbs and just how they are overcrowded.* I have found that planting them shoulder to shoulder is just fine and planting in layers is ok too.
It would probably be ok to separate them if you have the soil moist and not wet when you do this and don't forget to be extra attentive to moisture afterwards.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.