I usually sand the hell out if everything with 120 & 180 and it is surprising how smooth it can get without using 240 or higher.
That said, i still do a very, very light 240 just to catch any rough spots missed with coarser grit paper.
Those test samples would suggest you need to keep grain open as much as possible otherwise it may end up like a pastel white wash effect in your chosen stain colour.

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