Ok so when I buy my first case, I don't check about airflow at all..it has been 5 years and I want a new case
I'm interested in p360x but people generally says p360a has better airflow
Does p360x has really bad airflow that can break the PC component?
My first case is very cheap and probably don't have good airflow but my cpu and gpu still working fine ..so I'm just curious about airflow..is it important?
Generally, no. With any typical mATX cases and up, the difference in airflow is mostly non-fatal. Yes, some cases have abysmal airflow that pushes high-end components right against thermal throttle point, but some common sense when picking cases go a long way.
If, for instance, we're to put an overclocked FX 8350 along with GTX 480 in a Bitfenix Enso, we're just tempting fate at that point. High wattage components, in a case abysmal in its airflow department. If, say, a Haswell system and GTX 1650S is in the Enso instead, it'll probably get hot but not as critical as the FX system.
Basically any typical case with good side vents (so not just small cuts on the side) is decent enough. You can help it along with some optimal fans placement. See NZXT H500 and its counterintuitively solid panel front and its stock negative pressure setup. It's quite competitive in temps considering its use of solid panel and only perforated holes at the side for intake.
P360X seems to be a mediocre performer for airflow; but it's far from the worst. Venting on front panel can be better, but at least it seems like the top and side vents are useful. Some cases have decorative vents that don't do much for airflow. The P360X, on the other hand, is doable. You might want to experiment whether the front vents can help temps by intaking fresh air, or too obstructive and front intake fans would just recirculate warm air instead.
TL;DR: it's fine. 360X doesn't seem too bad.