After many attempts at contacting Sunflower Market on their coupon policy, I finally got a response! Yay! Here are some very basic information on their policy:
Sunflower Market accepts manufacturer coupons as long as they carry the item and the coupon is not expired.
Sunflower Market accepts Internet Printable coupons as long as they are not expired.
Sunflower Market does allow stacking a store coupon with a manufacturer coupon.
Sunflower Market does not accept manufacturer coupons that display another store’s logo.
Sunflower Market does not price-match or price-adjust.
I hope that helps to clear up any confusion that you may have had!