Triangle gives 2D planar rigidity, x/y, which is the direction most of the forces will come from but I imagine one could use gyroid and be fine as well? I've never tried it. I think secondly, when using the modifier, you have excellent z strength, simply because its 100% infill, with the modifier being where the triangles get used, with 30% infill. This provides excellent shear force resistance in X/Y directions. If you switch to gyroid or cubic for the modifier, expect better torsion but less localized stiffness in flat X/Y forces.
Z-direction = 100% dense => absorbs recoil and vertical stacking force.
X/Y regions = triangle infill => absorbs grip torsion, lateral mag force, and drop stresses.
Modifier limits extra infill to stress-critical areas only, keeping overall print efficient.
