How do the parties choose the exact place for carrying out the specific treaty, protocol, or agreement signing act? Can the place of treaty be considered a sign of something? What is the point of signing the treaty outside its participant countries?
Regarding only the 3rd part of the question:
What is the point of signing the treaty outside its participant countries?
It's rather like a first date between two apartment dwellers. The parties select some neutral safe location, (e.g. a local eatery), and try to find things they like and agree about, if possible; if not possible, the neutral location allows either party to depart at will.