I prefer Goretex which I use in the winter, my main jacket is also a Phoenix. In summer on wet days I use a Lowe Alpine Triple Point Ceramic Jacket which is light and more breathable. I also have a Berghaus Paclite Goretex jacket which is even lighter but has no liner whatsoever and during days of constant rain as I found out during my PW trip, the cold gets through quite quickly.
I would go for a lightweight Goretex system with a mesh lining.
Poncho's do not have any breathing ability and flap about in wind, but then maybe I am biased after years of getting by with bicycle capes as walkers did 50 years ago.