Yes, look at the position of your feet on a long climb. The soles of your mtb shoes might even have marks from the pedals. You can use that as a guide to set up clipless.
You might need a shim or some other special adjustment. I have big feet and I point my toes out when I ride. I have to use pedal extenders or my heels hit the crank.
If I try to force my feet straight it hurts my knees.