The metal gaskets work fine. I have adjusted valve clearances on hundreds of theses engines and have never changed a gasket, or had any problems afterwards. Never used sealer, never needed to. the only time gaskets get changed is when a manifold or head is renewed.
Sealer seems to cause more leaks than they cure. the only sealer you use is a small amount over the D shaped insert on the head just by the cam sprocket, and in the 90 degree corners by the cam bearing, both being on the rocker cover gasket.
Silver 2020 MR (4N15) Sportsbar, Towbar, EDS