Is it possible to achieve high opacity with white base inks using 2 strokes and 1 coating?
On a lighter shade substrates, it is possible.
On a dark colored substrates, it is possible but it may be difficult. This is because your 1 coat, 2 strokes print output would depend on the quality of your substrate (100% comb cotton vs polyester cotton), the kind of inks that is being used, the mesh count, mesh tension, squeegee durometer, squeegee profile, print strokes, angle, pressure, and the pull / push technique.
Also, ink viscosity can affect the print opacity. The higher the ink viscosity, the higher its opacity. This is because the inks sit on the substrate surface only and has not fully penetrated into its thread weave.
Hence, setting a too high viscosity ink base can affect the washing fastness, in lieu of its surface hold only.