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A pseudo-potential file of vasp has two energy-cutoffs (ENMIN and ENMAX) for the cutoff energy of plane wave. The vasp code does not guarantee the correct results are obtained if the energy-cutoff of plane-wave is smaller than ENIMN or larger than ENMAX. The large ENCUT make plane-wave base-set more completed but loss the accurate of pseudo-potential. There are exceptions that need increasing ENCUT such as in the calculations of stress tensor and the smooth P-V curves, but the ENCUT is still required no larger than 1.2-1.3 ENMAX to assure the correctness of pseudo-potential (See vasp manual) .

For orthorhombic structure, the k-points ixjxk is consistent with the shape of cell in real-space. The k-points mesh is proportional to 1/a,1/b,1/c.

I saw it from someone else. Is it right?

the results may be inaccurate if the the cutoff is too small, but increasing the cutoff may ALWAYS improve the results
(you must have misunderstood the manual ENCUT = 1.3* ENMAX is a good compromise to get accurate results
with a reasonably increased basis set size)