Hi- trying to figure out best way to do basement ceiling-drywall or ceiling tiles.. I have a lot of exposed pipes.. How much clearance do you need from floor joists to install a dropped ceiling? Also, is it really bad to "notch" the floor joists to stick the pipes and wires up? (having an argument with the BF that this will make the house/floor structurally weak) Please advise.. thanks

Our NC crawlspace is vented and damp. Two contractors have given different opinions as to what should be done and the prices are equivalent. #1. 20 mil poly on floors and walls with a $1600 dehumidifier, leaving fiberglass batts under floor above. #2. 14 mil poly on floors and walls, then cover walls with thermex board or spray insulation, take down fiberglass batts from under floor above, and use current HVAC system to provide some small conditioning of crawlspace air. Drainage is not a problem, but we do have some fungal growth that 2 contractor says will die off when area is closed. #1 contractor would clean off the fungal growth in addition to conditioning the space with the heavy liner and dehumidifier. Which solution is the better one, or are they equally good? Also, contractor 2 has told me that we have to store our lawn mower in the garage from now on, as it shouldn't be kept in a closed space. Thanks for helping!