Hey @jee
I might be on a similar journey as you, you can check my post Poor surface quality with dried original BL filament - I also went nuts over the calibration cards and it never quite came out as when I first unpacked my P2S a few days ago. Ultimately I now run the best with some aftermarket 0.4mm High Flow nozzle I tried for fun. So far I am quite happy and the under-extrusion got better using HF as well. Granted I use PETG HF filament as well, so that might factor in. But ultimately not using ironing actually creates smoother surfaces for me with more conformity.
Sorry I cannot provide a fix, just a different perspective. Fingers crossed you come closer to the result you are hoping for. I am also curious if and how you can improve the outcome! 