Labor tied to cost of material?

Hello Everyone, I am planning on doing a gut kitchen reno on an apartment I am soon closing on and will be looking at contractors soon(I've seen one already). Would the labor cost vary by the material? Say I'm installing Ikea cabinets instead of something fancier. Is it customary for the contractor to separate the cost on the proposal? The first contractor quoted me for labour and material when we never picked the material. Last but not least, I don't want to have a lot of contractors come in on different days since it's a crazy time for me at work, Can I meet a couple both at the same time and go through what I want and then just have submit their proposal to me? I don't know if there is some kind of etiquette involved. This is my first apartment, my first reno. thanks!