This is such basic stuff, but aside the primary role of bridging the sealer and the paint, I imagine another main function of the primer is to hide the grain of the wood.

Should my primed plugs show grain?

I should mention that I know it isn't essential that the grain be hid for a plug to be effective, but if I (personally) want a really clean look, I'm wondering what I can do to hide the grain.

Kind of wondering if a filler of some sort is needed for the results I'm looking for on woods like EWP(?)

Thanks in advance for any input.