to install Arch on a PC I have to make partition of the HDD
The swap is used by virtual memory, right? What's up if I make a too small or a too big swap partition? Could I have as result some kernel panic?
Actually you don't need the swap partition and the /boot partition.
But returning to your question: yes, the swap is used as virtual memory (and also for hibernation). If both the swap file and the physical RAM fill up, you most likely won't have a kernel panic: applications will just start to be killed by the kernel's out-of-memory killer.
But at this point your system will be unbearably slow (which might lead you to think that it has crashed) due to the heavy swapping.
If you have a too-big swap partition, it just won't be used and will be wasted disk space.