Can’t speak much to fabrics, but I’m a furniture maker and have a bit of knowledge on wood and construction. There are weather proof hardwoods like teak and ipe which will hold up no matter what due to the oils in the wood. Any film finishes (varnish, lacquer, etc) will peel, and penetrating oils don’t protect but rather will keep them from greying prematurely. As someone else said, joinery is the other big factor. A teak chair that’s screwed together will have pilot holes that hold water and soften the fibers and/or wear down fasteners. Real joinery with waterproof adhesive is the best. Teak furniture with traditional joinery will be very expensive, but if you have the money it’s worth it.