Ice and gutters

Good morning, I have a house with metal roofing that was installed by the prior owner approximately 10 years ago. Apparently he had some avalanching issues which caused great damage including the need to replace all gutters, plantings, etc.. Last season I installed 3 rows of snow guards( same manufacturer as the roofing) and used the contractor who had installed both the roof and the replacement gutters. I also had that contractor install "Gutter Tunnel" on all gutters.No problem until the recent snow in the East. I just lost all of my gutters again. I am going to replace but prior to going through that process I was looking for guidance as to size of gutters. installation considerations, product recommendations, basic do's and don'ts, etc... This is an expensive proposition and I would prefer not having to repeat again. Thank you for your feedback

Thanks