Need to make some improvements in my 100 yo attic with insulation, storage, and safety. Do you have any suggestions on how.

I would like to add some insulation and storage in my attic. I prefer DIY insulation preferably sheets that I can stick in between the studs, joists, and rafters.

there are nails poking down the roof. If I stick the insulation sheets in between the rafters would they just hold onto the nails?!

Also want to replace plywood sheets on joists. The old ones are worn down. Should I be placing insulation before placing the plywood?

What kind of DIY insulation is best for this location? Thank you