I would think the Newport will not be terribly firm and fast in May, but not terrible either.
Newport National is sort of Newport CC-lite...same idea, but modern. I would guess it's one of Arthur Hills's best efforts, and there are several places that make the course feel much older.
Misquamicut is a great layout, but one of the most private places in the US, on par with Myopia.
I think everything else worth mentioning in RI has been said...not much after NNational for publics, save for Triggs Memorial, the Ross muni in Providence, which is pretty neat. All the Ross privates are decent, even though I have only played Misquamicut and NCC. You can't go wrong with Metacomet, Sakonnet, Agawam Hunt, Wannamoisett, Potowamut, Wanumetonomy, or Point Judith...all are private though.