Quote is too generic without any detailed information. I would be wary of this contractor because later on they can/might claim "but I never wrote in the quotation!"

You know what? You're absolutely right! I have heard so many contractors say "the meat is in the VO". They give a quote that is so generic, and then when actually building, the owner ask, for example, "why this window so small?". The reply is "yes this is the size, if want to be bigger then must add RM xxxx". At that point the homeowner has no choice but to pay extra. What's the owner going to do? Finish the renovations, and then find another contractor, break the window and install a bigger one?