Parallax does not concern the clarity of your reticle.
Reticle focus is determined by the Ocular (eye side) focus.
Parallax is the placement of two images, target and reticle, at the same focal point.
You check parallax not by the clarity of your reticle but by moving your head slightly to see if the reticle and target do not stay stable - ie the aimpoint of your reticle does not stay glued to the desired point of impact on your target.
Look at a wall switch.
Place your pointer finger in contact on the tip of the switch and move your head.
No matter where you move your head you view your finger in contact with the tip of the wall switch.
Now move your index finger to a point half the distance between your eye and the wall switch.
Place the image of the tip of your finger on the tip of the wall switch, think of your finger tip as a front sight post, place it on the end of the switch.
Now move your head - the finger tip and end of switch do not maintain "contact".
Yes. Ilya Koshkin has a video somewhere that discusses how medium power and smaller reticle image allows a finer focus. As you are experiencing, a large image has a wide range of diopter focus.
Ahead of the arrival of my ZCO 527 today on the brown truck, I was researching this subject a little bit in an effort to get the most out the optic. I heard ZCO recommends setting the focus at the lowest magnification within the range. I had previously been told the opposite and to use max...
You can get by with a reticle somewhat out of focus, your eye will do the adjustment.
The downside is eye fatigue over time. Ideally your eye does no work beyond seeing when looking down the tube.
More important you get your parallax as tight as possible and again don't sweat that so much if you have good mechanics and consistent interface with the rifle.