Roof Needed; Exposed Fastener Roofs in Ice Damming Conway, NH

Roof Needed; Exposed Fastener Roofs in Ice Damming Conway, NH We live in Conway, NH area and subject to ice damming, and after seeing several roofing contractors for required metal roof over existing shingles with very different points of view, as a consumer it is confusing… can you HELP? - We are on a budget right now and the Standing seam roof is best; but we need to understand IF we can use panels without issues PLEASE? - We were told that Screw-Down Style panels are good with specific suppliers and IF used with treated screws with “rubber type” washer and covering metal washer; is that true? - What are the deficiencies of these types of exposed fastener roofs; longevity of these types of washers; will these eventually leak, and do they require maintenance? - What needs to be done specifically with using panels at a low slope of 2:12 farmers porch if using panels? (butyl, ice guard, etc ?) - What should be considered in trying to seal the laps on panels; is butyl only required on low slope and sealing of edges OR the whole roof? - How long will the sealants between laps perform under yearly severe weather? - What types of maintenance would you recommend to this style of roof to prevent leakage from expansion and contraction and ice damming around the laps? IF too much info requested; can you advise of references to determine these answers or best contacts to discuss PLEASE?