> Honest question, is the UN bureaucracy that different from the big international NGOs?

It very much depends on the bureaucracy but there are quite a few UN agencies with actual authority far beyond what any NGO would have (with the exception of the International Committee of the Red Cross which is explicitly given authority by the Geneva Convention).

For example the WHO is backed by other international treaties like the International Health Regulations (~196 signatories) that give it various powers like declaring a public health emergency. Its executive board is full of Ministers of Health, Directors-General of national health services, and other high ranking public health officials that directly exercise their powers within their respective governments.

There’s also the International Court of Justice, IMF, International Atomic Energy Agency, ICAO (aviation), IMO (maritime), and ITU (telecom) with various powers ranging from allocating spectrum to handing out billions in bailout loans.

The UN may not be able to enforce many of its rulings and decisions without a standing army but for the most part, many agencies do have a lot of authority backed by international law to actually do stuff beyond coordinating its member nations and few countries ever rock the boat. Out of the agencies I mentioned above the ICJ is really the only one that has the rare bit of trouble because noncompliance escalates to the Security Council where appeals die due to friendly vetoes.