I have dodgy knees. Compared to (Shimano) road SPDs, mountain bike SPDs have a lot more float. It’s pretty hard to set them up badly to be honest, so not sure of the value of a shop adjustment.
I ride with my heels kicked in, so angle mine slightly towards my big toe, but with the amount of float available it’s a pretty crude adjustment.
I did find Egg Beaters offered so much uncontrolled float, it actually made my knees worse. It’s also worth checking your saddle position (and height). You should be able to drop a plumb line from your kneecap to the ball of your foot. Knee too far forwards or backwards will put extra strain on parts of your body.