“Ride Checkpoint Requirement- License Insurance Registration”

So when we are stopped by police at a RIDE checkpoint, the first thing I always ask them is "What is the purpose of this stop?"

Usually I get a response along the lines of "looking for drunk/impaired drivers".

Now I know I do NOT have to answer any questions they ask me, so whatever the ask I just say "I am legally not required to answer any of your questions and have no comment."

So of course, although perfectly legal, police do not like this.

Since I asked what the purpose of the stop was initially, can they still ask to see my license and registration and insurance, or do they need some kind of grounds/probable cause that I am either impaired or have an unsafe vehicle before they can do that?

I completely understand that some higher court has said it is okay for police to violate our charter rights in certain circumstances (of course I completely disagree with that decision, but that is a different discussion). And checking for valid drivers license/insurance/registration is one of them, and checking for an unsafe vehicle is another, and checking if you have been drinking I think is the last reason.

QUESTION:

Are police allowed to check my license/insurance/registration, or the safety of my vehicle if the only reason they gave me for the stop was "looking for impaired drivers"? Do they have to be specific about which of the things they are checking?

Thanks