China has already targeted Serbia and Montenegro - infrastructure mainly. I can't find the source now, but I have heard they already started investing in Hungary.

I don't know much about Hungary so could you provide a reason why it is bad "if EU lets China come into Hungary"? Unless it is because China Bad, then I'm not interested, but I'm hoping for something more interesting than that. Personally I would hate to see EU close in on itself and so it needs to align with outsiders. China seems just as good a partner as the other big markets to me.

Cue the Orbanites saying how the EU wants to interfere in "matters of their country"

This (and the events of January 6th) are a good reminder that the law is worth the paper it's printed on if no one acts on it.