I want to bring PC + PS, in a separate flight though.
Can I carry it as hand-luggage or check it in as luggage and mark it as fragile? Do I need to pack it with special box (maybe wooden box)?
Or is it depend on destination and departing country?
For carry-on, electronics are allowed and the only consideration is the weight/size limits for carry-on baggage set by the airline. As long as the electronics fit within those limits you should be fine. A Playstation should, for example, easily be small enough. A PC might be another matter, depending on the size of the case.
You can of course put it into checked luggage. But there is, unfortunately, little guarantee about the treatment it will receive. Aside from the possibility that it'll be damaged, there is also a chance it will go missing, either by accident are theft (the chances of theft varies greatly).
It is usually not recommended to put fragile or valuable (i.e. likely to be stolen) items in check-in baggage if you can at all avoid it. At minimum you should pack it in such a way that it can sustain some degree of rough handling without the contents being damaged.