I usually travel highway 97, that's Oroville / Osoyoos ( US / CA ) going south, usually Hi, why ya going, how long? over 10 grand? have a good day.
coming back home ( north ) I am often asked about gun/ammo purchases, fruits, vegetables, meats and Milk and Dairy products, do a lot of shopping just across the line, never had a problem with US cheese, but I also don't bring 10 packs at a time over same with butter, however I have been sitting in line and watched them haul gallon milk jugs ( and quarts) out of cars and RV's back to back.
it also seems to depend on who is on gate duty,once in line at the crossing, DONT change lanes, I watched one guy wave 20 cars thrue, the other lane full search open doors, full interview, watched a guy leave the lane and move to the fast moving one, and into Inspections he went.
as others have said, take off your hat, sunglasses answer questions with basic yes no direct answers, passports ready to hand over, then keep hands where they can see them, be yourself and usually no problems.