Type of Wood

[takagari]

for your fist question. "last" is relative you wont get the years from wood that you would get from a plastic rack

that being said, woods much cheaper.
The lightest option would be good both side plywood (pricey!) and then stain it.

give it a good seal. most people how ever use covered melamine. seal the ends. you should be able to get a few years from that but it is heavier.

I think i'm going to suck it up and have a plastic rack made. for my own sanity. lol